Hand-supportable code symbol reader employing coplanar laser illumination and linear imaging

ABSTRACT

A hand-supportable planar laser illumination and imaging (PLIIM) based code symbol reader includES: a hand-supportable housing having light transmission aperture; a linear image formation and detection module having a linear image detection array; and a planar laser illumination beam (PLIB) producing device having at least one visible laser diode (VLD) for producing a planar light illumination beam (PLIB). The code symbol reader further includes image grabber for grabbing digital linear images formed and detected by the image formation and detection module, an image data buffer for buffering the digital linear images grabbed by the image grabber and constructing a two-dimensional image from a series of buffered linear digital images, and an image processing computer for processing the buffered two-dimensional digital image so as to read code symbols graphically represented in the two-dimensional digital linear image. During object illumination and imaging operations, a controller automatically controls the linear image formation and detection module, the PLIB producing device, the image frame grabber, and the image data buffer.

CROSS-REFERENCE TO RELATED U.S. APPLICATIONS

This is a Continuation of copending U.S. application Ser. No. 11/490,544filed Jul. 20, 2006; which is a Continuation of copending U.S.application Ser. No. 11/484,369 filed Jul. 11, 2006; which is aContinuation of U.S. application Ser. No. 10/066,545 filed Feb. 1, 2002,now U.S. Pat. No. 7,073,718 B2; which is a Continuation of U.S.application Ser. No. 09/721,885 filed Nov. 24, 2000, now U.S. Pat. No.6,631,842; which is a Continuation-in-Part of copending application Ser.No. 09/327,756 filed Jun. 7, 1999, now abandoned; and PCT/US00/15624filed Jun. 7, 2000, published as WO 00/75856 A1; each said applicationbeing commonly owned by Assignee, Metrologic Instruments, Inc., ofBlackwood, N.J., and incorporated herein by reference as if fully setforth herein.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates generally to an improved method of andsystem for illuminating the surface of objects during image formationand detection operations, and also to an improved method of and systemfor producing digital images using such improved methods of objectillumination.

2. Brief Description of the Prior Art

The use of image-based bar code symbol readers and scanners is wellknown in the field of auto-identification. Examples of image-based barcode symbol reading/scanning systems include, for example, hand-handscanners, point-of-sale (POS) scanners, and industrial-type conveyorscanning systems.

Presently, most commercial image-based bar code symbol readers areconstructed using charge-coupled device (CCD) image sensing/detectingtechnology. Unlike laser-based scanning technology, CCD imagingtechnology has particular illumination requirements which differ fromapplication to application.

Most prior art CCD-based image scanners, employed in conveyor-typepackage identification systems, require high-pressure sodium, metalhalide or halogen lamps and large, heavy and expensive parabolic orelliptical reflectors to produce sufficient light intensities toilluminate the large depth of field scanning fields supported by suchindustrial scanning systems. Even when the light from such lamps iscollimated or focused using such reflectors, light strikes the targetobject other than where the imaging optics of the CCD-based camera areviewing. Since only a small fraction of the lamps output power is usedto illuminate the CCD camera's field of view, the total output power ofthe lamps must be very high to obtain the illumination levels requiredalong the field of view of the CCD camera. The balance of the outputillumination power is simply wasted in the form of heat.

Most prior art CCD-based hand-held image scanners use an array of lightemitting diodes (LEDs) to flood the field of view of the imaging opticsin such scanning systems. A large percentage of the output illuminationfrom these LED sources is dispersed to regions other than the field ofview of the scanning system. Consequently, only a small percentage ofthe illumination is actually collected by the imaging optics of thesystem, Examples of prior art CCD hand-held image scanners employing LEDillumination arrangements are disclosed in US Pat. Nos. Re. 36,528,5,777,314, 5,756,981, 5,627,358, 5,484,994, 5,786,582, and 6,123,261 toRoustaei, each assigned to Symbol Technologies, Inc. and incorporatedherein by reference in its entirety. In such prior art CCD-basedhand-held image scanners, an array of LEDs are mounted in a scanninghead in front of a CCD-based image sensor that is provided with acylindrical lens assembly. The LEDs are arranged at an angularorientation relative to a central axis passing through the scanning headso that a fan of light is emitted through the light transmissionaperture thereof that expands with increasing distance away from theLEDs. The intended purpose of this LED illumination arrangement is toincrease the “angular distance” and “depth of field” of CCD-based barcode symbol readers. However, even with such improvements in LEDillumination techniques, the working distance of such hand-held CCDscanners can only be extended by using more LEDs within the scanninghead of such scanners to produce greater illumination output therefrom,thereby increasing the cost, size and weight of such scanning devices.

Similarly, prior art “hold-under” and “hands-free presentation” typeCCD-based image scanners suffer from shortcomings and drawbacks similarto those associated with prior art CCD-based hand-held image scanners.

Thus, there is a great need in the art for an improved method of andsystem for illuminating the surface of objects during image formationand detection operations, and also an improved method of and system forproducing digital images using such improved methods objectillumination, while avoiding the shortcomings and drawbacks of prior artillumination, imaging and scanning systems and methodologies.

OBJECTS AND SUMMARY OF THE PRESENT INVENTION

Accordingly, a primary object of the present invention is to provide animproved method of and system for illuminating the surface of objectsduring image formation and detection operations and also improvedmethods of and systems for producing digital images using such improvedmethods object illumination, while avoiding the shortcomings anddrawbacks of prior art systems and methodologies.

Another object of the present invention is to provide such an improvedmethod of and system or device for illuminating the surface of objectsusing a linear array of laser light emitting devices configured togetherto produce a substantially planar beam of laser illumination whichextends in substantially the same plane as the field of view of thelinear array of electronic image detection cells of the system, along atleast a portion of its optical path within its working distance,

Another object of the present invention is to provide such an imageproducing system, wherein the linear array of electronic image detectioncells are realized using charge-coupled device (CCD) technology.

Another object of the present invention is to provide such an improvedmethod of and system for producing digital images of objects using avisible laser diode array for producing a planar laser illumination beamfor illuminating the surfaces of such objects, and also an electronicimage detection array for detecting laser light reflected off theilluminated objects during illumination and imaging operations.

Another object of the present invention is to provide such an improvedmethod of and system for illuminating the surfaces of object to beimaged, using an array of planar laser illumination arrays which employVLDs that are smaller, and cheaper, run cooler, draw less power, havelonger lifetimes, and require simpler optics (because their frequencybandwidths are very small compared to the entire spectrum of visiblelight).

Another object of the present invention is to provide such an improvedmethod of and system for illuminating the surfaces of objects to beimaged, wherein the VLD concentrates all of its output power into a thinlaser beam illumination plane which spatially coincides exactly with thefield of view of the imaging optics of the system, so very little lightenergy is wasted.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein the working distance ofthe system can be easily extended by simply changing the beam focusingand imaging optics, and without increasing the output power of thevisible laser diode (VLD) sources employed therein.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein each planar laserillumination beam is focused so that the minimum width thereof (e.g. 0.6mm along its non-spreading direction) occurs at a point or plane whichis the farthest object distance at which the system is designed tocapture images.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein a fixed focal lengthimaging subsystem is employed, and the laser beam focusing technique ofthe present invention helps compensate for decreases in the powerdensity of the incident planar illumination beam due to the fact thatthe width of the planar laser illumination beam for increasing distancesaway from the imaging subsystem.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein a variable focal length(i.e. zoom) imaging subsystem is employed, and the laser beam focusingtechnique of the present invention helps compensate for (i) decreases inthe power density of the incident illumination beam due to the fact thatthe width of the planar laser illumination beam (i.e. beamwidth) alongthe direction of the beam's planar extent increases for increasingdistances away from the imaging subsystem, and (ii) any 1/r² type lossesthat would typically occur when using the planar laser illumination beamof the present invention.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein scanned objects needonly be illuminated along a single plane which is coplanar with a planarsection of the field of view of the image formation and detection modulebeing used in the PLIIM system.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein the planar laserillumination technique of the present invention enables high-speedmodulation of the planar laser illumination beam, and use of simple(i.e. substantially monochromatic) lens designs for substantiallymonochromatic optical illumination and image formation and detectionoperations.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein the planar laserillumination beam and the field of view of the image formation anddetection module do not overlap on any optical surface within the PLIIMsystem.

Another object of the present invention is to provide a planar laserillumination and imaging (PLIIM) system, wherein the planar laserillumination beams are permitted to spatially overlap with the FOV ofthe imaging lens of the PLIIM only outside of the system housing,measured at a particular point beyond the light transmission window,through which the FOV is projected.

Another object of the present invention is to provide a planar laserillumination (PLIM) system for use in illuminating objects being imaged.

Another object of the present invention is to provide planar laserillumination and substantially-monochromatic imaging system, wherein themonochromatic imaging module is realized as an array of electronic imagedetection cells (e.g. CCD).

Another object of the present invention is to provide a planar laserillumination and substantially-monochromatic imaging system, wherein theplanar laser illumination arrays (PLIAs) and the image formation anddetection (IFD) module are mounted in strict optical alignment on anoptical bench such that there is substantially no relative motion,caused by vibration or temperature changes, is permitted between theimaging lens within the IFD module and the VLD/cylindrical lensassemblies within the PLIAs.

Another object of the present invention is to provide a planar laserillumination and substantially-monochromatic imaging system, wherein theimaging module is realized as a photographic image recording module.

Another object of the present invention is to provide a planar laserillumination and substantially-monochromatic imaging system, wherein theimaging module is realized as an array of electronic image detectioncells (e.g. CCD) having short integration time settings for high-speedimage capture operations.

Another object of the present invention is to provide a planar laserillumination and substantially-monochromatic imaging system, wherein apair of planar laser illumination arrays are mounted about an imageformation and detection module having a field of view, so as to producea substantially planar laser illumination beam which is coplanar withthe field of view during object illumination and imaging operations.

Another object of the present invention is to provide a planar laserillumination and substantially-monochromatic imaging system, theprinciple of Gaussian summation of light intensity distributions isemployed to produce a planar laser illumination beam having a powerdensity across the width the beam which is substantially the same forboth far and near fields of the system.

Another object of the present invention is to provide method of andsystem for illuminating the surfaces of objects during image formationand detection operations.

Another object of the present invention is to provide method of andsystem for producing digital images of objects using planar laserillumination beams and electronic image detection arrays.

Another object of the present invention is to provide method of andsystem for producing a planar laser illumination beam to illuminate thesurface of objects and electronically detecting light reflected off theilluminated objects during planar laser beam illumination operations.

Another object of the present invention is to provide a hand-heldcoplanar laser illuminated image detection and processing system ordevice for use in reading bar code symbols and other character strings.

Another object of the present invention is to provide method of andsystem for producing images of objects by focusing a planar laserillumination beam within the field of view of an imaging lens so thatthe minimum width thereof along its non-spreading direction occurs atthe farthest object distance of the imaging lens.

Another object of the present invention is to provide such system inwhich lasers beams having multiple wavelengths are used to sensepackages having a wide range of reflectivity characteristics.

Another object of the present invention is to provide improvedimage-based hand-held scanners, body-wearable scanners,presentation-type scanners, and hold-under scanners which embody thePLIIM subsystem of the present invention.

As will be described in greater detail in the Detailed Description ofthe Illustrative Embodiments set forth below, such objectives areachieved in novel methods of and systems for illuminating objects (e.g.bar coded packages, textual materials, graphical indicia, etc.) usingplanar laser illumination beams having substantially-planar spatialdistribution characteristics that extend through the field of view (FOV)of image formation and detection modules (e.g. realized within aCCD-type digital electronic camera employed in such systems.

In each illustrative embodiment of the present invention, thesubstantially planar laser illumination beams are preferably producedfrom a planar laser illumination beam array (PLIA) comprising anplurality of planar laser illumination modules (PLIMs). Each PLIMcomprises a visible laser diode (VLD, a focusing lens, and a cylindricaloptical element arranged therewith. The individual planar laserillumination beam components produced from each PLIM are opticallycombined within the PLIA to produce a composite substantially planarlaser illumination beam having substantially uniform power densitycharacteristics over the entire spatial extend thereof and thus theworking range of the system.

Preferably, each planar laser illumination beam component is focused sothat the minimum beam width thereof occurs at a point or plane which isthe farthest or maximum object distance at which the system is designedto acquire images. In the case of both fixed and variable focal lengthimaging systems, this inventive principle helps compensate for decreasesin the power density of the incident planar laser illumination beam dueto the fact that the width of the planar laser illumination beamincreases in length for increasing object distances away from theimaging subsystem.

By virtue of the novel principles of the present invention, it is nowpossible to use both VLDs and high-speed CCD-type image detectors inconveyor, hand-held and hold-under type scanning applications alike,enjoying the advantages and benefits that each such technology has tooffer, while avoiding the shortcomings and drawbacks hitherto associatedtherewith.

These and other objects of the present invention will become apparenthereinafter and in the Claims to Invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, thefollowing Detailed Description of the Illustrative Embodiment should beread in conjunction with the accompanying Drawings, wherein:

FIG. 1A is a schematic representation of a first generalized embodimentof the planar laser illumination and (electronic) imaging (PLIIM) systemof the present invention, wherein a pair of planar laser illuminationarrays (PLIAs) are mounted on opposite sides of a linear (i.e.1-dimensional) type image formation and detection module (IFDM) having afixed focal length imaging lens, a fixed focal distance and fixed fieldof view, such that the planar illumination array produces a stationary(i.e. non-scanned) plane of laser beam illumination which is disposedsubstantially coplanar with the field of view of the image formation anddetection module during object illumination and image detectionoperations carried out by the PLIIM system on a moving bar code symbolor other graphical structure;

FIG. 1B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, wherein the field of view of the image formation and detectionmodule is folded in the downwardly imaging direction by the field ofview folding mirror so that both the folded field of view and resultingstationary planar laser illumination beams produced by the planarillumination arrays are arranged in a substantially coplanarrelationship during object illumination and image detection operations;

FIG. 1B2 is a schematic representation of the PLIIM system shown in FIG.1A, wherein the linear image formation and detection module is showncomprising a linear array of photo-electronic detectors realized usingCCD technology, and each planar laser illumination array is showncomprising an array of planar laser illumination modules;

FIG. 1C is a schematic representation of a single planar laserillumination module (PLIM) used to construct each planar laserillumination array shown in FIG. 1B, wherein the planar laserillumination beam emanates substantially within a single plane along thedirection of beam propagation towards an object to be opticallyilluminated;

FIG. 1D is a schematic diagram of the planar laser illumination moduleof FIG. 1C, shown comprising a visible laser diode (VLD), a lightcollimating lens, and a cylindrical-type lens element configuredtogether to produce a beam of planar laser illumination;

FIG. 1E1 is a plan view of the VLD, collimating lens and cylindricallens assembly employed in the planar laser illumination module of FIG.1C, showing that the focused laser beam from the collimating lens isdirected on the input side of the cylindrical lens, and the output beamproduced therefrom is a planar laser illumination beam expanded (i.e.spread out) along the plane of propagation;

FIG. 1E2 is an elevated side view of the VLD, collimating lens andcylindrical lens assembly employed in the planar laser illuminationmodule of FIG. 1C, showing that the laser beam is transmitted throughthe cylindrical lens without expansion in the direction normal to theplane of propagation, but is focused by the collimating lens at a pointresiding within a plane located at the farthest object distancesupported by the PLIIM system;

FIG. 1F is a block schematic diagram of the PLIIM system shown in FIG.1A, comprising a pair of planar illumination arrays, a linear-type imageformation and detection module, a stationary field of view foldingmirror, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 1G1 is a schematic representation of an exemplary realization ofthe PLIIM system of FIG. 1A, shown comprising a linear image formationand detection module, a pair of planar laser illumination arrays, and afield of view (FOV) folding mirror for folding the fixed field of viewof the linear image formation and detection module in a direction thatis coplanar with the plane of laser illumination beams produced by theplanar laser illumination arrays;

FIG. 1G2 is a plan view schematic representation of the PLIIM system,taken along line 1G2-1G2 in FIG. 1G1, showing the spatial extent of thefixed field of view of the linear image formation and detection modulein the illustrative embodiment of the present invention;

FIG. 1G3 is an elevated end view schematic representation of the PLIIMsystem, taken along line 1G3-1G3 in FIG. 1G1, showing the fixed field ofview of the linear image formation and detection module being folded inthe downwardly imaging direction by the field of view folding mirror,and the planar laser illumination beam produced by each planar laserillumination module being directed in the imaging direction such thatboth the folded field of view and planar laser illumination beams arearranged in a substantially coplanar relationship during objectillumination and image detection operations;

FIG. 1G4 is an elevated side view schematic representation of the PLIIMsystem, taken along line 1G4-1G4 in FIG. 1G1, showing the field of viewof the image formation and detection module being folded in thedownwardly imaging direction by the field of view folding mirror, andthe planar laser illumination beam produced by each planar laserillumination module being directed along the imaging direction such thatboth the folded field of view and stationary planar laser illuminationbeams are arranged in a substantially coplanar relationship duringobject illumination and image detection operations;

FIG. 1G5 is an elevated side view of the PLIIM system of FIG. 1G1,showing the spatial limits of the fixed field of view (FOV) of the imageformation and detection module when set to image the tallest packagesmoving on a conveyor belt structure, as well as the spatial limits ofthe fixed FOV of the image formation and detection module when set toimage objects having height values close to the surface height of theconveyor belt structure;

FIG. 1G6 is a perspective view of a first type of light shield which canbe used in the PLIIM system of FIG. 1G1, to visually block portions ofplanar laser illumination beams that extend beyond the scanning field ofthe system, but which could pose a health risk to humans if viewedthereby during system operation;

FIG. 1G7 is a perspective view of a second type of light shield whichcan be used in the PLIIM system of FIG. 1G1, to visually block portionsof planar laser illumination beams that extend beyond the scanning fieldof the system, but which could pose a health risk to humans if viewedthereby during system operation;

FIG. 1G8 is a perspective view of one planar laser illumination array(PLIA) employed in the PLIIM system of FIG. 1G1, showing an array ofvisible laser diodes (VLDs), each mounted within a VLD mounting blockwherein a focusing lens is mounted and on the end of which there is av-shaped notch or recess, within which a cylindrical lens element ismounted, and wherein each such VLD mounting block is mounted on anL-bracket for mounting within the housing of the PLIIM system;

FIG. 1G9 is an elevated end view of one planar laser illumination array(PLIA) employed in the PLIIM system of FIG. 1G1, taken along line1G9-1G9 thereof;

FIG. 1G10 is an elevated side view of one planar laser illuminationarray (PLIA) employed in the PLIIM system of FIG. 1G1, taken along line1G10-1G10 thereof, showing a visible laser diode (VLD) and a focusinglens mounted within a VLD mounting block, and a cylindrical lens elementmounted at the end of the VLD mounting block, so that the central axisof the cylindrical lens element is substantially perpendicular to theoptical axis of the focusing lens;

FIG. 1G11 is an elevated side view of one of the VLD mounting blocksemployed in the PLIIM system of FIG. 1G1, taken along a viewingdirection which is orthogonal to the central axis of the cylindricallens element mounted to the end portion of the VLD mounting block;

FIG. 1G12 is an elevated plan view of one of VLD mounting blocksemployed in the PLIIM system of FIG. 1G1, taken along a viewingdirection which is parallel to the central axis of the cylindrical lenselement mounted to the VLD mounting block;

FIG. 1H1 is an elevated side view of the collimating lens elementinstalled within each VLD mounting block employed in the PLIIM system ofFIG. 1G1;

FIG. 1H2 is an axial view of the collimating lens element installedwithin each VLD mounting block employed in the PLIIM system of FIG. 1G1;

FIG. 1I1 is an elevated plan view of one of planar laser illuminationmodules (PLIMs) employed in the PLIIM system of FIG. 1G1, taken along aviewing direction which is parallel to the central axis of thecylindrical lens element mounted in the VLD mounting block thereof,showing that the cylindrical lens element expands (i.e. spreads out) thelaser beam along the direction of beam propagation so that asubstantially planar laser illumination beam is produced, which ischaracterized by a plane of propagation that is coplanar with thedirection of beam propagation;

FIG. 1I2 is an elevated plan view of one of the PLIMs employed in thePLIIM system of FIG. 1G1, taken along a viewing direction which isperpendicular to the central axis of the cylindrical lens elementmounted within the axial bore of the VLD mounting block thereof, showingthat the focusing lens planar focuses the laser beam to its minimum beamwidth at a point which is the farthest distance at which the system isdesigned to capture images, while the cylindrical lens element does notexpand or spread out the laser beam in the direction normal to the planeof propagation of the planar laser illumination beam;

FIG. 1J1 is a geometrical optics model for the imaging subsystememployed in the linear-type image formation and detection module in thePLIIM system of the first generalized embodiment shown in FIG. 1A;

FIG. 1J2 is a geometrical optics model for the imaging subsystem andlinear image detection array employed in linear-type image detectionarray employed in the image formation and detection module in the PLIIMsystem of the first generalized embodiment shown in FIG. 1A;

FIG. 1J3 is a graph, based on thin lens analysis, showing that the imagedistance at which light is focused through a thin lens is a function ofthe object distance at which the light originates;

FIG. 1J4 is a schematic representation of an imaging subsystem having avariable focal distance lens assembly, wherein a group of lens can becontrollably moved along the optical axis of the subsystem, and havingthe effect of changing the image distance to compensate for a change inobject distance, allowing the image detector to remain in place;

FIG. 1J5 is schematic representation of a variable focal length (zoom)imaging subsystem which is capable of changing its focal length over agiven range; so that a longer focal length produces a smaller field ofview at a given object distance;

FIG. 1J6 is a schematic representation of an illustrative embodiment ofthe image formation and detection (IFD) module employed in the PLIIMsystems of the present invention, wherein various optical parametersused to model the system are defined and graphically indicated whereverpossible;

FIG. K1 is a schematic representation illustrating how the field of viewof a PLIIM system can be fixed to substantially match the scan fieldwidth thereof (measured at the top of the scan field) at a substantialdistance above a conveyor belt;

FIG. 1K2 is a schematic representation illustrating how the field ofview of a PLIIM system can be fixed to substantially match the scanfield width of a low profile scanning field slightly above the conveyorbelt surface, by fixed the focal length of the imaging subsystem duringthe optical design stage;

FIG. 1L is a schematic representation illustrating how an arrangement ofFOV beam folding mirrors can be used to produce an expanded FOV thatmatches the geometrical characteristics of the scanning application athand, when the FOV emerges from the system housing;

FIG. 1L2 is a schematic representation illustrating how the fixed fieldof view of an imaging subsystem can be expanded across a working space(e.g. conveyor belt structure) by rotating the FOV during objectillumination and imaging operations;

FIG. 1M1 shows a data plot of pixel power density E_(pix) vs. objectdistance r calculated using the arbitrary but reasonable values E₀=1W/m², f=80 mm and F=4.5, demonstrating that, in a counter-intuitivemanner, the power density at the pixel (and therefore the power incidenton the pixel, since its area remains constant) actually increases as theobject distance increases;

FIG. 1M2 is data plot of laser beam power density vs. position along theplanar laser beam width showing that the total output power in theplanar laser illumination beam of the present invention is distributedalong the width of the beam in a roughly Gaussian distribution;

FIG. 1M3 shows a plot of beam width length L vs. object distance rcalculated using a beam fan/spread angle θ=50°, demonstrating that theplanar laser beam width increases as a function of increasing objectdistance;

FIG. 1M4 is a typical data plot of planar laser beam height h vs. imagedistance r for a planar laser illumination beam of the present inventionfocused at the farthest working distance in accordance with theprinciples of the present invention, demonstrating that the heightdimension of the planar laser beam decreases as a function of increasingobject distance;

FIG. 1N is a data plot of planar laser beam power density E₀ at thecenter of its beam width, plotted as a function of object distance,demonstrating that use of the laser beam focusing technique of thepresent invention, wherein the height of the planar laser illuminationbeam is decreased as the object distance increases, compensates for theincrease in beam width in the planar laser illumination beam, whichoccurs for an increase in object distance, thereby yielding a laser beampower density on the target object which increases as a function ofincreasing object distance over a substantial portion of the objectdistance range of the PLIIM system;

FIG. 1O is a data plot of pixel power density E₀ vs. object distance,obtained when using a planar laser illumination beam whose beam heightdecreases with increasing object distance, and also a data plot of the“reference” pixel power density plot E_(pix) vs. object distanceobtained when using a planar laser illumination beam whose beam heightis substantially constant (e.g. 1 mm) over the entire portion of theobject distance range of the PLIIM system;

FIG. 1P1 is a schematic representation of the composite power densitycharacteristics associated with the planar laser illumination array inthe PLIIM system of FIG. 1G1, taken at the “near field region” of thesystem, and resulting from the additive contributions of the individualvisible laser diodes in the planar laser illumination arrays;

FIG. 1P2 is a schematic representation of the composite power densitycharacteristics associated with the planar laser illumination array inthe PLIIM system of FIG. 1G1, taken at the “far field region” of thesystem, and resulting from the additive contributions of the individualvisible laser diodes in the planar laser illumination arrays;

FIG. 1Q1 is a schematic representation of second illustrative embodimentof the PLIIM system of the present invention shown in FIG. 1A, showncomprising a linear image formation and detection module, and a pair ofplanar laser illumination arrays arranged in relation to the imageformation and detection module such that the field of view thereof isoriented in a direction that is coplanar with the plane of thestationary planar laser illumination beams produced by the planar laserillumination arrays, without using any laser beam or field of viewfolding mirrors;

FIG. 1Q2 is a block schematic diagram of the PLIIM system shown in FIG.1Q1, comprising a linear image formation and detection module, a pair ofplanar laser illumination arrays, an image frame grabber, an image databuffer, a decode image processor, and a system controller;

FIG. 1R1 is a schematic representation of third illustrative embodimentof the PLIIM system of the present invention shown in FIG. 1A, showncomprising a linear image formation and detection module having a fieldof view, a pair of planar laser illumination arrays for producing firstand second stationary planar laser illumination beams, and a pair ofstationary planar laser beam folding mirrors arranged so as to fold theoptical paths of the first and second planar laser illumination beamssuch that the planes of the first and second stationary planar laserillumination beams are in a direction that is coplanar with the field ofview of the image formation and detection module;

FIG. 1R2 is a block schematic diagram of the PLIIM system shown in FIG.1P1, comprising a linear image formation and detection module, astationary field of view folding mirror, a pair of planar illuminationarrays, a pair of stationary planar laser illumination beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 1S1 is a schematic representation of fourth illustrative embodimentof the PLIIM system of the present invention shown in FIG. 1A, showncomprising a linear image formation and detection module having a fieldof view (FOV), a stationary field of view (FOV) folding mirror forfolding the field of view of the image formation and detection module, apair of planar laser illumination arrays for producing first and secondstationary planar laser illumination beams, and a pair of stationaryplanar laser illumination beam folding mirrors for folding the opticalpaths of the first and second stationary planar laser illumination beamsso that planes of first and second stationary planar laser illuminationbeams are in a direction that is coplanar with the field of view of theimage formation and detection module;

FIG. 1S2 is a block schematic diagram of the PLIIM system shown in FIG.1S1, comprising a linear-type image formation and detection module, astationary field of view folding mirror, a pair of planar laserillumination arrays, a pair of stationary planar laser beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 1T is a schematic representation of an under (or over) the-conveyorbelt package identification system embodying the PLIIM system of FIG.1A;

FIG. 1U is a schematic representation of a hand-supportable bar codesymbol reading system embodying the PLIIM system of FIG. 1A;

FIG. 1V1 is a is a schematic representation of second generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear type image formation and detection module (IFDM)having a field of view, such that the planar laser illumination arraysproduce a plane of laser beam illumination (i.e. light) which isdisposed substantially coplanar with the field of view of the imageformation and detection module, and that the planar laser illuminationbeam and the field of view of the image formation and detection modulemove synchronously while maintaining their coplanar relationship witheach other as the planar laser illumination beam is automaticallyscanned over a 2-D region of space during object illumination and imagedetection operations;

FIG. 1V2 is a schematic representation of first illustrative embodimentof the PLIIM system of the present invention shown in FIG. 1V1, showncomprising an image formation and detection module having a field ofview (FOV), a field of view (FOV) folding/sweeping mirror for foldingthe field of view of the image formation and detection module, a pair ofplanar laser illumination arrays for producing first and second planarlaser illumination beams, and a pair of planar laser beamfolding/sweeping mirrors, jointly or synchronously movable with the FOVfolding/sweeping mirror, and arranged so as to fold and sweep theoptical paths of the first and second planar laser illumination beams,so that the folded field of view of the image formation and detectionmodule is synchronously moved with the planar laser illumination beamsin a direction that is coplanar therewith as the planar laserillumination beams are scanned over a 2-D region of space under thecontrol of the system controller;

FIG. 1V3 is a block schematic diagram of the PLIIM system shown in FIG.1V1, comprising a pair of planar illumination arrays, a pair of planarlaser beam folding/sweeping mirrors, a linear-type image formation anddetection module, a field of view folding/sweeping mirror, an imageframe grabber, an image data buffer, a decode image processor, and asystem controller;

FIG. 1V4 is a schematic representation of an over-the-conveyor beltpackage identification system embodying the PLIIM system of FIG. 1V1;

FIG. 1V5 is a schematic representation of a presentation-type bar codesymbol reading system embodying the PLIIM system of FIG. 1V1;

FIG. 2A is a schematic representation of a third generalized embodimentof the PLIIM system of the present invention, wherein a pair of planarlaser illumination arrays (PLIAs) are mounted on opposite sides of alinear (i.e. 1-dimensional) type image formation and detection module(IFDM) having a fixed focal length imaging lens, a variable focaldistance and a fixed field of view (FOV), so that the planar laserillumination arrays produce a plane of laser beam illumination which isdisposed substantially coplanar with the field view of the imageformation and detection module during object illumination and imagedetection operations carried out on bar code symbol structures and othergraphical indicia which may embody information within its structure;

FIG. 2B1 is a schematic representation of a first illustrativeembodiment of the PLIIM system shown in FIG. 2A, comprising an imageformation and detection module having a field of view (FOV), and a pairof planar laser illumination arrays for producing first and secondstationary planar laser illumination beams in an imaging direction thatis coplanar with the field of view of the image formation and detectionmodule;

FIG. 2B2 is a schematic representation of the PLIIM system of thepresent invention shown in FIG. 2B1, wherein the linear image formationand detection module is shown comprising a linear array ofphoto-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

FIG. 2C1 is a block schematic diagram of the PLIIM system shown in FIG.2B1, comprising a pair of planar illumination arrays, a linear-typeimage formation and detection module, an image frame grabber, an imagedata buffer, a decode image processor, and a system controller;

FIG. 2C2 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2B1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 2D1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2A, shown comprising a linear image formation and detection module, astationary field of view (FOV) folding mirror for folding the field ofview of the image formation and detection module, and a pair of planarlaser illumination arrays arranged in relation to the image formationand detection module such that the folded field of view is oriented inan imaging direction that is coplanar with the stationary planes oflaser illumination produced by the planar laser illumination arrays;

FIG. 2D2 is a block schematic diagram of the PLIIM system shown in FIG.2D1, comprising a pair of planar laser illumination arrays (PLIAs), alinear-type image formation and detection module, a stationary field ofview of folding mirror, an image frame grabber, an image data buffer, adecode image processor, and a system controller;

FIG. 2D3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLLIM system shownin FIG. 2D1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 2E1 is a schematic representation of the third illustrativeembodiment of the PLIIM system of the present invention shown in FIG.1A, shown comprising an image formation and detection module having afield of view (FOV), a pair of planar laser illumination arrays forproducing first and second stationary planar laser illumination beams, apair of stationary planar laser beam folding mirrors for folding thestationary (i.e. non-swept) planes of the planar laser illuminationbeams produced by the pair of planar laser illumination arrays, in animaging direction that is coplanar with the stationary plane of thefield of view of the image formation and detection module during systemoperation;

FIG. 2E2 is a block schematic diagram of the PLIIM system shown in FIG.2B1, comprising a pair of planar laser illumination arrays, a linearimage formation and detection module, a pair of stationary planar laserillumination beam folding mirrors, an image frame grabber, an image databuffer, a decode image processor, and a system controller;

FIG. 2E3 is a schematic representation of the linear image formation anddetection module (IFDM) employed in the PLIIM system shown in FIG. 2B1,wherein an imaging subsystem having fixed focal length imaging lens, avariable focal distance and a fixed field of view is arranged on anoptical bench, mounted within a compact module housing, and responsiveto focus control signals generated by the system controller of the PLIIMsystem;

FIG. 2F1 is a schematic representation of the fourth illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a stationary field of view (FOV) foldingmirror, a pair of planar laser illumination arrays for producing firstand second stationary planar laser illumination beams, and a pair ofstationary planar laser beam folding mirrors arranged so as to fold theoptical paths of the first and second stationary planar laserillumination beams so that these planar laser illumination beams areoriented in an imaging direction that is coplanar with the folded fieldof view of the linear image formation and detection module;

FIG. 2F2 is a block schematic diagram of the PLIIM system shown in FIG.2F1, comprising a pair of planar illumination arrays, a linear imageformation and detection module, a stationary field of view (FOV) foldingmirror, a pair of stationary planar laser illumination beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 2F3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 2F1, wherein an imaging subsystem having a fixed focal lengthimaging lens, a variable focal distance and a fixed field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 2G is a schematic representation of an over-the-conveyor beltpackage identification system embodying the PLIIM system of FIG. 2A;

FIG. 2H is a schematic representation of a hand-supportable bar codesymbol reading system embodying the PLIIM system of FIG. 2A;

FIG. 2I1 is a schematic representation of the fourth generalizedembodiment of the PLIIM system of the present invention, wherein a pairof planar laser illumination arrays (PLIAs) are mounted on oppositesides of a linear image formation and detection module (IFDM) having afixed focal length imaging lens, a variable focal distance and fixedfield of view (FOV), so that the planar illumination arrays produces aplane of laser beam illumination which is disposed substantiallycoplanar with the field view of the image formation and detection moduleand synchronously moved therewith while the planar laser illuminationbeams are automatically scanned over a 2-D region of space during objectillumination and imaging operations;

FIG. 2I2 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.2I1, shown comprising an image formation and detection module having afield of view (FOV), a field of view (FOV) folding/sweeping mirror, apair of planar laser illumination arrays for producing first and secondplanar laser illumination beams, and a pair of planar laser beamfolding/sweeping mirrors, jointly movable with the FOV folding/sweepingmirror, and arranged so that the field of view of the image formationand detection module is coplanar with the folded planes of first andsecond planar laser illumination beams, and the coplanar FOV and planarlaser illumination beams are synchronously moved together while theplanar laser illumination beams and FOV are scanned over a 2-D region ofspace containing a stationary or moving bar code symbol or othergraphical structure (e.g. text) embodying information;

FIG. 2I3 is a block schematic diagram of the PLIIM system shown in FIGS.2I1 and 2I2, comprising a pair of planar illumination arrays, a linearimage formation and detection module, a field of view (FOV)folding/sweeping mirror, a pair of planar laser illumination beamfolding/sweeping mirrors jointly movable therewith, an image framegrabber, an image data buffer, a decode image processor, and a systemcontroller;

FIG. 2I4 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIGS. 2I1 and 2I2, wherein an imaging subsystem having a fixed focallength imaging lens, a variable focal distance and a fixed field of viewis arranged on an optical bench, mounted within a compact modulehousing, and responsive to focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 2I5 is a schematic representation of a hand-supportable bar codesymbol reader embodying the PLIIM system of FIG. 2I1;

FIG. 2I6 is a schematic representation of a presentation-type bar codesymbol reader embodying the PLIIM system of FIG. 2I1;

FIG. 3A is a schematic representation of a fifth generalized embodimentof the PLIIM system of the present invention, wherein a pair of planarlaser illumination arrays (PLIAs) are mounted on opposite sides of alinear image formation and detection module (IFDM) having a variablefocal length imaging lens, a variable focal distance and a variablefield of view, so that the planar laser illumination arrays produce astationary plane of laser beam illumination (i.e. light) which isdisposed substantially coplanar with the field view of the imageformation and detection module during object illumination and imagedetection operations carried out on bar code symbol and other graphicalindicia by the PLIIM system of the present invention;

FIG. 3B1 is a schematic representation of the first illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising an image formation and detection module, and a pairof planar laser illumination arrays arranged in relation to the imageformation and detection module such that the stationary field of viewthereof is oriented in an imaging direction that is coplanar with thestationary plane of laser illumination produced by the planar laserillumination arrays, without using any laser beam or field of viewfolding mirrors.

FIG. 3B2 is a schematic representation of the first illustrativeembodiment of the PLIIM system shown in FIG. 3B1, wherein the linearimage formation and detection module is shown comprising a linear arrayof photo-electronic detectors realized using CCD technology, and eachplanar laser illumination array is shown comprising an array of planarlaser illumination modules;

FIG. 3C1 is a block schematic diagram of the PLIIM shown in FIG. 3B1,comprising a pair of planar laser illumination arrays, a linear imageformation and detection module, an image frame grabber, an image databuffer, a decode image processor, and a system controller;

FIG. 3C2 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3B1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 3D is a schematic representation of a preferred implementation ofthe imaging subsystem contained in the image formation and detectionmodule employed in the PLIIM system of FIG. 3B1, shown comprising astationary lens system mounted before the stationary linear imagedetection array, a first movable lens system for large stepped movementrelative to the stationary lens system during image zooming operations,and a second movable lens system for small stepped movements relative tothe first movable lens system and the stationary lens system duringimage focusing operations;

FIG. 3E1 is a schematic representation of the second illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection module, apair of planar laser illumination arrays, and a stationary field of view(FOV) folding mirror arranged in relation to the image formation anddetection module such that the stationary field of view thereof isoriented in an imaging direction that is coplanar with the stationaryplane of laser illumination produced by the planar laser illuminationarrays, without using any planar laser illumination beam foldingmirrors;

FIG. 3E2 is a block schematic diagram of the PLIIM system shown in FIG.3E1, comprising a pair of planar illumination arrays, a linear imageformation and detection module, a stationary field of view (FOV) foldingmirror, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 3E3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3E1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system;

FIG. 3E4 is a schematic representation of the PLIIM system of FIG. 3E1,shown comprising a linear-type image formation and detection module, apair of planar laser illumination arrays, and a field of view (FOV)folding mirror for folding the field of view of the image formation anddetection module in a direction that is coplanar with the plane of laserillumination produced by the planar illumination arrays;

FIG. 3E5 is a plan view schematic representation of the PLIIM system,taken along line 3E5-3E5 in FIG. 3E4, showing the spatial extent of thefield of view of the image formation and detection module in theillustrative embodiment of the present invention;

FIG. 3E6 is an elevated end view schematic representation of the PLIIMsystem, taken along line 3E6-3E6 in FIG. 3E4, showing the field of viewof the linear image formation and detection module being folded in thedownwardly imaging direction by the field of view folding mirror, andthe planar laser illumination beam produced by each planar laserillumination module being directed in the imaging direction such thatboth the folded field of view and planar laser illumination beams arearranged in a substantially coplanar relationship during objectillumination and imaging operations;

FIG. 3E7 is an elevated side view schematic representation of the PLIIMsystem, taken along line 3E7-3E7 in FIG. 3E4, showing the field of viewof the linear image formation and detection module being folded in thedownwardly imaging direction by the field of view folding mirror, andthe planar laser illumination beam produced by each planar laserillumination module being directed along the imaging direction such thatboth the folded field of view and stationary planar laser illuminationbeams are arranged in a substantially coplanar relationship duringobject illumination and image detection operations;

FIG. 3E8 is an elevated side view of the PLIIM system of FIG. 3E4,showing the spatial limits of the variable field of view (FOV) of thelinear image formation and detection module when controllably adjustedto image the tallest packages moving on a conveyor belt structure, aswell as the spatial limits of the variable FOV of the linear imageformation and detection module when controllably adjusted to imageobjects having height values close to the surface height of the conveyorbelt structure;

FIG. 3F1 is a schematic representation of the third illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a pair of planar laser illumination arraysfor producing first and second stationary planar laser illuminationbeams, a pair of stationary planar laser illumination beam foldingmirrors arranged relative to the planar laser illumination arrays so asto fold the stationary planar laser illumination beams produced by thepair of planar illumination arrays in an imaging direction that iscoplanar with stationary field of view of the image formation anddetection module during illumination and imaging operations;

FIG. 3F2 is a block schematic diagram of the PLIIM system shown in FIG.3FF1, comprising a pair of planar illumination arrays, a linear imageformation and detection module, a pair of stationary planar laserillumination beam folding mirrors, an image frame grabber, an image databuffer, a decode image processor, and a system controller;

FIG. 3F3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3F1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

FIG. 3G1 is a schematic representation of the fourth illustrativeembodiment of the PLIIM system of the present invention shown in FIG.3A, shown comprising a linear image formation and detection modulehaving a field of view (FOV), a pair of planar laser illumination arraysfor producing first and second stationary planar laser illuminationbeams, a stationary field of view (FOV) folding mirror for folding thefield of view of the image formation and detection module, and a pair ofstationary planar laser beam folding mirrors arranged so as to fold theoptical paths of the first and second planar laser illumination beamssuch that stationary planes of first and second planar laserillumination beams are in an imaging direction which is coplanar withthe field of view of the image formation and detection module duringillumination and imaging operations;

FIG. 3G2 is a block schematic diagram of the PLIIM system shown in FIG.3G1, comprising a pair of planar illumination arrays, a linear imageformation and detection module, a stationary field of view (FOV) foldingmirror, a pair of stationary planar laser illumination beam foldingmirrors, an image frame grabber, an image data buffer, a decode imageprocessor, and a system controller;

FIG. 3G3 is a schematic representation of the linear type imageformation and detection module (IFDM) employed in the PLIIM system shownin FIG. 3G1, wherein an imaging subsystem having a variable focal lengthimaging lens, a variable focal distance and a variable field of view isarranged on an optical bench, mounted within a compact module housing,and responsive to zoom and focus control signals generated by the systemcontroller of the PLIIM system during illumination and imagingoperations;

FIG. 3H is a schematic representation of an over-the-conveyor andside-of conveyor belt package identification systems embodying the PLIIMsystem of FIG. 3A; and

FIG. 3I is a schematic representation of a hand-supportable bar codesymbol reading device embodying the PLIIM system of FIG. 3A.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS OF THE PRESENTINVENTION

Referring to the figures in the accompanying Drawings, the preferredembodiments of the Planar Laser Illumination and (Electronic) Imaging(PLIIM) System of the present invention will be described in greatdetail, wherein like elements will be indicated using like referencenumerals.

Overview of the Planar Laser Illumination and Electronic Imaging (PLIIM)System of the Present Invention

In accordance with the principles of the present invention, an object(e.g. a bar coded package, textual materials, graphical indicia, etc.)is illuminated by a substantially planar laser illumination beam havingsubstantially-planar spatial distribution characteristics along a planardirection which passes through the field of view (FOV) of an imageformation and detection module (e.g. realized within a CCD-type digitalelectronic camera, or a 35 mm optical-film photographic camera), whileimages of the illuminated object are formed and detected by the imageformation and detection module.

This inventive principle of coplanar laser illumination and imageformation is embodied in two different classes of the PLIIM, namely: (1)in PLIIM systems shown in FIGS. 1A, 1V1, 2A, 2I1, 3A, and 3J1, whereinthe image formation and detection modules in these systems employlinear-type (1-D) image detection arrays; and (2) in PLIIM systems shownin FIGS. 4A, 5A and 6A, wherein the image formation and detectionmodules in these systems employ area-type (2-D) image detection arrays.Among these illustrative systems, those shown in FIGS. 1A, 2A and 3Aeach produce a planar laser illumination beam that is neither scannednor deflected relative to the system housing during planar laserillumination and image detection operations and thus can be said to use“stationary” planar laser illumination beams to read relatively movingbar code symbol structures and other graphical indicia. Those systemsshown in FIGS. 1V1, 2I1, 3J1, 4A, 5A and 6A, each produce a planar laserillumination beam that is scanned (i.e. deflected) relative to thesystem housing during planar laser illumination and image detectionoperations and thus can be said to use “moving” planar laserillumination beams to read relatively stationary bar code symbolstructures and other graphical indicia.

In each such system embodiment, it is preferred that each planar laserillumination beam is focused so that the minimum beam width thereof(e.g. 0.6 mm along its non-spreading direction, as shown in FIG. 1I2)occurs at a point or plane which is the farthest or maximum working(i.e. object) distance at which the system is designed to acquire imagesof objects, as best shown in FIG. 1I2. Hereinafter, this aspect of thepresent invention shall be deemed the “Focus Beam At Farthest ObjectDistance (FBAFOD)” principle.

In the case where a fixed focal length imaging subsystem is employed inthe PLIIM system, the FBAFOD principle helps compensate for decreases inthe power density of the incident planar laser illumination beam due tothe fact that the width of the planar laser illumination beam increasesin length for increasing object distances away from the imagingsubsystem.

In the case where a variable focal length (i.e. zoom) imaging subsystemis employed in the PLIIM system, the FBAFOD principle helps compensatefor (i) decreases in the power density of the incident planarillumination beam due to the fact that the width of the planar laserillumination beam increases in length for increasing object distancesaway from the imaging subsystem, and (ii) any 1/r² type losses thatwould typically occur when using the planar laser planar illuminationbeam of the present invention.

By virtue of the present invention, scanned objects need only beilluminated along a single plane which is coplanar with a planar sectionof the field of view of the image formation and detection module (e.g.camera) during illumination and imaging operations carried out by thePLIIM system. This enables the use of low-power, light-weight,high-response, ultra-compact, high-efficiency solid-state illuminationproducing devices, such as visible laser diodes (VLDs), to selectivelyilluminate ultra-narrow sections of an object during image formation anddetection operations, in contrast with high-power, low-response,heavy-weight, bulky, low-efficiency lighting equipment (e.g. sodiumvapor lights) required by prior art illumination and image detectionsystems. In addition, the planar laser illumination techniques of thepresent invention enables high-speed modulation of the planar laserillumination beam, and use of simple (i.e. substantially-monochromaticwavelength) lens designs for substantially-monochromatic opticalillumination and image formation and detection operations.

As will be illustrated in greater detail hereinafter, PLIIM systemsembodying the “planar laser illumination” and “FBAFOD” principles of thepresent invention can be embodied within a wide variety of bar codesymbol reading and scanning systems, as well as optical character, text,and image recognition systems well known in the art.

In general, bar code symbol reading systems can be grouped into at leasttwo general scanner categories, namely: industrial scanners; andpoint-of-sale (POS) scanners.

An industrial scanner is a scanner that has been designed for use in awarehouse or shipping application where large numbers of packages mustbe scanned in rapid succession. Industrial scanners includeconveyor-type scanners, and hold-under scanners. These scannercategories will be described in greater detail below

Conveyor scanners are designed to scan packages as they move by on aconveyor belt. In general, a minimum of six conveyors (e.g. one overheadscanner, four side scanners, and one bottom scanner) are necessary toobtain complete coverage of the conveyor belt and ensure that any labelwill be scanned no matter where on a package it appears. Conveyorscanners can be further grouped into top, side, and bottom scannerswhich will be briefly summarized below.

Top scanners are mounted above the conveyor belt and look down at thetops of packages transported therealong. It might be desirable to anglethe scanner's field of view slightly in the direction from which thepackages approach or that in which they recede depending on the shapesof the packages being scanned. A top scanner generally has less severedepth of field and variable focus or dynamic focus requirements comparedto a side scanner as the tops of packages are usually fairly flat, atleast compared to the extreme angles that a side scanner might have toencounter during scanning operations.

Side scanners are mounted beside the conveyor belt and scan the sides ofpackages transported therealong. It might be desirable to angle thescanner's field of view slightly in the direction from which thepackages approach or that in which they recede depending on the shapesof the packages being scanned and the range of angles at which thepackages might be rotated.

Side scanners generally have more severe depth of field and variablefocus or dynamic focus requirements compared to a top scanner because ofthe great range of angles at which the sides of the packages may beoriented with respect to the scanner (this assumes that the packages canhave random rotational orientations; if an apparatus upstream on the onthe conveyor forces the packages into consistent orientations, thedifficulty of the side scanning task is lessened). Because side scannerscan accommodate greater variation in object distance over the surface ofa single target object, side scanners can be mounted in the usualposition of a top scanner for applications in which package tops areseverely angled.

Bottom scanners are mounted beneath the conveyor and scans the bottomsof packages by looking up through a break in the belt that is covered byglass to keep dirt off the scanner. Bottom scanners generally do nothave to be variably or dynamically focused because its working distanceis roughly constant, assuming that the packages are intended to be incontact with the conveyor belt under normal operating conditions.However, boxes tend to bounce around as they travel on the belt, andthis behavior can be amplified when a package crosses the break, whereone belt section ends and another begins after a gap of several inches.For this reason, bottom scanners must have a large depth of field toaccommodate these random motions, to which a variable or dynamic focussystem could not react quickly enough.

Hold-under scanners are designed to scan packages that are picked up andheld underneath it. The package is then manually routed or otherwisehandled, perhaps based on the result of the scanning operation.Hold-under scanners are generally mounted so that its viewing optics areoriented in downward direction, like a library bar code scanner. Depthof field (DOF) is an important characteristic for hold-under scanners,because the operator will not be able to hold the package perfectlystill while the image is being acquired.

Point-of-sale (POS) scanners are typically designed to be used at aretail establishment to determine the price of an item being purchased.POS scanners are generally smaller than industrial scanner models, withmore artistic and ergonomic case designs. Small size, low weight,resistance to damage from accident drops and user comfort are all majordesign factors for POS scanner. POS scanners include hand-held scanners,hands-free presentation scanners and combination-type scannerssupporting both hands-on and hands-free modes of operation. Thesescanner categories will be described in greater detail below.

Hand-held scanners are designed to be picked up by the operator andaimed at the label to be scanned.

Hands-free presentation scanners are designed to remain stationary andhave the item to be scanned picked up and passed in front of thescanning device. Presentation scanners can be mounted on counterslooking horizontally, embedded flush with the counter lookingvertically, or partially embedded in the counter looking vertically, buthaving a “tower” portion which rises out above the counter and lookshorizontally to accomplish multiple-sided scanning. If necessary,presentation scanners that are mounted in a counter surface can alsoinclude a scale to measure weights of items.

Some POS scanners can be used as handheld units or mounted in stands toserve as presentation scanners, depending on which is more convenientfor the operator based on the item that must be scanned.

Various generalized embodiments of the PLIIM system of the presentinvention will now be described in great detail, and after eachgeneralized embodiment, various applications thereof will be described.

First Generalized Embodiment of the PLIIM System of the PresentInvention

The first generalized embodiment of the PLIIM system of the presentinvention 1 is illustrated in FIG. 1A. As shown therein, the PLIIMsystem 1 comprises: a housing 2 of compact construction; a linear (i.e.1-dimensional) type image formation and detection (IFD) 3 including a1-D electronic image detection array 3A, and a linear (1-D) imagingsubsystem (LIS) 3B having a fixed focal length, a fixed focal distance,and a fixed field of view (FOV), for forming a 1-D image of anilluminated object 4 located within the fixed focal distance and FOVthereof and projected onto the 1-D image detection array 3A, so that the1-D image detection array 3A can electronically detect the image formedthereon and automatically produce a digital image data set 5representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 3, such that each planarlaser illumination array 6A and 6B produces a plane of laser beamillumination 7A, 7B which is disposed substantially coplanar with thefield view of the image formation and detection module 3 during objectillumination and image detection operations carried out by the PLIIMsystem.

An image formation and detection (IFD) module 3 having an imaging lenswith a fixed focal length has a constant angular field of view (FOV);that is, the imaging subsystem can view more of the target object'ssurface as the target object is moved further away from the IFD module.A major disadvantage to this type of imaging lens is that the resolutionof the image that is acquired, expressed in terms of pixels or dots perinch (dpi), varies as a function of the distance from the target objectto the imaging lens. However, a fixed focal length imaging lens iseasier and less expensive to design and produce than a zoom-type imaginglens which will be discussed in detail hereinbelow with reference toFIGS. 3A through 3J4.

The distance from the imaging lens 3B to the image detecting (i.e.sensing) array 3A is referred to as the image distance. The distancefrom the target object 4 to the imaging lens 3B is called the objectdistance. The relationship between the object distance (where the objectresides) and the image distance (at which the image detection array ismounted) is a function of the characteristics of the imaging lens, andassuming a thin lens, is determined by the thin (imaging) lens equation(1) defined below in greater detail. Depending on the image distance,light reflected from a target object at the object distance will bebrought into sharp focus on the detection array plane. If the imagedistance remains constant and the target object is moved to a new objectdistance, the imaging lens might not be able to bring the lightreflected off the target object (at this new distance) into sharp focus.An image formation and detection (IFD) module having an imaging lenswith fixed focal distance cannot adjust its image distance to compensatefor a change in the target's object distance; all the component lenselements in the imaging subsystem remain stationary. Therefore, thedepth of field (DOF) of the imaging subsystems alone must be sufficientto accommodate all possible object distances and orientations. Suchbasic optical terms and concepts will be discussed in more formal detailhereinafter with reference to FIGS. 1J1 and 1J6.

In accordance with the present invention, the planar laser illuminationarrays 6A and 6B, the linear image formation and detection module 3, andany non-moving FOV and/or planar laser illumination beam folding mirrorsemployed in any particular system configuration described herein, arefixedly mounted on an optical bench 8 or chassis so as to prevent anyrelative motion (which might be caused by vibration or temperaturechanges) between: (i) the image forming optics (e.g. imaging lens)within the image formation and detection module 3 and any stationary FOVfolding mirrors employed therewith; and (ii) each planar laserillumination array (i.e. VLD/cylindrical lens assembly) 6A, 6B and anyplanar laser illumination beam folding mirrors employed in the PLIIMsystem configuration. Preferably, the chassis assembly should providefor easy and secure alignment of all optical components employed in theplanar laser illumination arrays 6A and 6B as well as the imageformation and detection module 3, as well as be easy to manufacture,service and repair. Also, this PLIIM system 1 employs the general“planar laser illumination” and “focus beam at farthest object distance(FBAFOD)” principles described above. Various illustrative embodimentsof this generalized PLIIM system will be described below.

First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

The first illustrative embodiment of the PLIIM system 1A of FIG. 1A isshown in FIG. 1B1. As illustrated therein, the field of view of theimage formation and detection module 3 is folded in the downwardlydirection by a field of view (FOV) folding mirror 9 so that both thefolded field of view 10 and resulting first and second planar laserillumination beams 7A and 7B produced by the planar illumination arrays6A and 6B, respectively, are arranged in a substantially coplanarrelationship during object illumination and image detection operations.One primary advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to installed within a compartment (or cavity) of a housing havingrelatively low height dimensions. Also, in this system design, there isa relatively high degree of freedom provided in where the imageformation and detection module 3 can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to practiced in a relatively easy manner.

The PLIIM system 1A illustrated in FIG. 1B1 is shown in greater detailin FIG. 1B2. As shown therein, the linear image formation and detectionmodule 3 is shown comprising an imaging subsystem 3B, and a linear arrayof photo-electronic detectors 3A realized using high-speed CCDtechnology (e.g. Dalsa IT-P4 Linear Image Sensors, from Dalsa, Inc.located on the WWW at http://www.dalsa.com). As shown, each planar laserillumination array 6A, 6B comprises a plurality of planar laserillumination modules (PLIMs) 11A through 11F, closely arranged relativeto each other, in a rectilinear fashion. For purposes of clarity, eachPLIM is indicated by reference numeral. As shown in FIGS. 1K1 and 1K2,the relative spacing of each PLIM is such that the spatial intensitydistribution of the individual planar laser beams superimpose andadditively provide a substantially uniform composite spatial intensitydistribution for the entire planar laser illumination array 6A and 6B.

FIG. 1C is a schematic representation of a single planar laserillumination module (PLIM) 11 used to construct each planar laserillumination array 6A, 6B shown in FIG. 1B2. As shown in FIG. 1C, theplanar laser illumination beam emanates substantially within a singleplane along the direction of beam propagation towards an object to beoptically illuminated.

As shown in FIG. 1D, the planar laser illumination module of FIG. 1C,comprises: a visible laser diode (VLD) 13 supported within an opticaltube or block 14; a light collimating lens 15 supported within theoptical tube 14; and a cylindrical-type lens element 16 configuredtogether to produce a beam of planar laser illumination 12. As shown inFIG. 1E, a focused laser beam 17 from the focusing lens 15 is directedon the input side of the cylindrical lens element 16, and the producedoutput therefrom is a planar laser illumination beam 12.

As shown in FIG. 1F, the PLIIM system 1A of FIG. 1A comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of PLMS 11Athrough 11F, and each PLIM being driven by a VLD driver circuit 18 wellknown in the art; linear-type image formation and detection module 3;field of view (FOV) folding mirror 9, arranged in spatial relation withthe image formation and detection module 3; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer, includingimage-based bar code symbol decoding software such as, for example,SwiftDecode™ Bar Code Decode Software, from Omniplanar, Inc., ofPrinceton, N.J. (http://www.omniplanar.com); and a system controller 22operably connected to the various components within the system forcontrolling the operation thereof in an orchestrated manner.

Detailed Description of an Exemplary Realization of the PLIIM SystemShown in FIG. 1B1 Through 1F

Referring now to FIGS. 1G1 through 1N2, an exemplary realization of thePLIIM system shown in FIGS. 1B1 through 1F will now be described indetail below.

As shown in FIGS. 1G1 and 1G2, the PLIIM system 25 of the illustrativeembodiment is contained within a compact housing 26 having height,length and width dimensions 45″, 21.7″, and 19.7″ to enable easymounting above a conveyor belt structure or the like. As shown in FIG.1G1, the PLIIM system comprises an image formation and detection module3, a pair of planar laser illumination arrays 6A, 6B, and a stationaryfield of view (FOV) folding structure (e.g. mirror, refractive element,or diffractive element) 9, as shown in FIGS. 1B1 and 1B2. The functionof the FOV folding mirror 9 is to fold the field of view (FOV) of theimage formation and detection module 3 in a direction that is coplanarwith the plane of laser illumination beams 7A and 7B produced by theplanar illumination arrays 6A and 6B respectively. As shown, components6A, 6B, 3 and 9 are fixedly mounted to an optical bench 8 supportedwithin the compact housing 26 by way of metal mounting brackets thatforce the assembled optical components to vibrate together on theoptical bench. In turn, the optical bench is shock mounted to the systemhousing techniques which absorb and dampen shock forces and vibration.The 1-D CCD imaging array 3A can be realized using a variety ofcommercially available high-speed line-scan camera systems such as, forexample, the Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com. Notably, image framegrabber 17, image data buffer (e.g. VRAM) 20, decode image processor 21,and system controller 22 are realized on one or more printed circuit(PC) boards contained within a camera and system electronic module 27also mounted on the optical bench, or elsewhere in the system housing 26

In general, the linear CCD image detection array (i.e. sensor) 3A has asingle row of pixels, each of which measures from several μm to severaltens of μm along each dimension. Square pixels are most common, and mostconvenient for bar code scanning applications, but different aspectratios are available. In principle, a linear CCD detection array can seeonly a small slice of the target object it is imaging at any given time.For example, for a linear CCD detection array having 2000 pixels, eachof which is 10 μm square, the detection array measures 2 cm long by 10μm high. If the imaging lens 3B in front of the linear detection array3A causes an optical magnification of 10×, then the 2 cm length of thedetection array will be projected onto a 20 cm length of the targetobject. In the other dimension, the 10 μm height of the detection arraybecomes only 100 μm when projected onto the target. Since any label tobe scanned will typically measure more than a hundred μm or so in eachdirection, capturing a single image with a linear image detection arraywill be inadequate. Therefore, in practice, the linear image detectionarray employed in each of the PLIIM systems shown in FIGS. 1A through3J6 builds up a complete image of the target object by assembling aseries of linear (1-D) images, each of which is taken of a differentslice of the target object. Therefore, successful use of a linear imagedetection array in the PLIIM systems shown in FIGS. 1A through 3J6requires relative movement between the target object and the PLIIMsystem. In general, either the target object is moving and the PLIIMsystem is stationary, or else the field of view of PLIIM system is sweptacross a relatively stationary target object, as shown in FIGS. 3J1through 3J4. This makes the linear image detection array a naturalchoice for conveyor scanning applications.

As shown in FIG. 1G1, the compact housing 26 has a relatively long lighttransmission window 28 of elongated dimensions for projecting the FOV ofthe image formation and detection module 3 through the housing towards apredefined region of space outside thereof, within which objects can beilluminated and imaged by the system components on the optical bench 8.Also, the compact housing 26 has a pair of relatively short lighttransmission apertures 29A and 29B closely disposed on opposite ends oflight transmission window 28, with minimal spacing therebetween, asshown in FIG. 1G1, so that the FOV emerging from the housing 26 canspatially overlap in a coplanar manner with the substantially planarlaser illumination beams projected through transmission windows 29A and29B, as close to transmission window 28 as desired by the systemdesigner, as shown in FIGS. 1G3 and 1G4. Notably, in some applications,it is desired for such coplanar overlap between the FOV and planar laserillumination beams to occur very close to the light transmission windows20, 29A and 29B (i.e. at short optical throw distances), but in otherapplications, for such coplanar overlap to occur at large optical throwdistances.

In either event, each planar laser illumination array 6A and 6B isoptically isolated from the FOV of the image formation and detectionmodule 3. In the preferred embodiment, such optical isolation isachieved by providing a set of opaque wall structures 30A 30B about eachplanar laser illumination array, from the optical bench 8 to its lighttransmission window 29A or 29B, respectively. Such optical isolationstructures prevent the image formation and detection module 3 fromdetecting any laser light transmitted directly from the planar laserillumination arrays 6A, 6B within the interior of the housing. Instead,the image formation and detection module 3 can only receive planar laserillumination that has been reflected off an illuminated object, andfocused through the imaging subsystem of module 3.

As shown in FIG. 1G3, each planar laser illumination array 6A, 6Bcomprises a plurality of planar laser illumination modules 11A through11F, each individually and adjustably mounted to an L-shaped bracket 32which, in turn, is adjustably mounted to the optical bench. As mentionedabove, each planar laser illumination module 11 must be rotatablyadjustable within its L-shaped bracket so as permit easy yet secureadjustment of the position of each PLIM 11 along a common alignmentplane extending within L-bracket portion 32A thereby permitting precisepositioning of each PLIM relative to the optical axis of the imageformation and detection module 3. Once properly adjusted in terms ofposition on the L-bracket portion 32A, each PLIM can be securely lockedby an allen or like screw threaded into the body of the L-bracketportion 32A. Also, L-bracket portion 32B, supporting a plurality ofPLIMS 11A through 11B, is adjustably mounted to the optical bench 8 andreleasably locked thereto so as to permit precise lateral and/or angularpositioning of the L-bracket 32B relative to the optical axis and FOV ofthe image formation and detection module 3. The function of suchadjustment mechanisms is to enable the intensity distributions of theindividual PLIMs to be additively configured together along asubstantially singular plane, typically having a width or thicknessdimension on the orders of the width and thickness of the spread ordispersed laser beam within each PLIM. When properly adjusted, thecomposite planar laser illumination beam will exhibit substantiallyuniform power density characteristics over the entire working range ofthe PLIIM system, as shown in FIGS. 1K1 and 1K2.

In FIG. 1G3, the exact position of the individual PLIMs 11A through 11Falong its L-bracket 32A is indicated relative to the optical axis of theimaging lens 3B within the image formation and detection module 3. FIG.1G3 also illustrates the geometrical limits of each substantially planarlaser illumination beam produced by its corresponding PLIM, measuredrelative to the folded FOV 10 produced by the image formation anddetection module 3. FIG. 1G4, illustrates how, during objectillumination and image detection operations, the FOV of the imageformation and detection module 3 is first folded by FOV folding mirror19, and then arranged in a spatially overlapping relationship with theresulting/composite planar laser illumination beams in a coplanar mannerin accordance with the principles of the present invention.

Notably, the PLIIM system of FIG. 1G1 has an image formation anddetection module with an imaging subsystem having a fixed focal distancelens and a fixed focusing mechanism. Thus, such a system is best used ineither hand-held scanning applications, and/or bottom scanningapplications where bar code symbols and other structures can be expectedto appear at a particular distance from the imaging subsystem. In FIG.1G5, the spatial limits for the FOV of the image formation and detectionmodule are shown for two different scanning conditions, namely: whenimaging the tallest package moving on a conveyor belt structure; andwhen imaging objects having height values close to the surface of theconveyor belt structure. In a PLIIM system having a fixed focal distancelens and a fixed focusing mechanism, the PLIIM system would be capableof imaging objects under one of the two conditions indicated above, butnot under both conditions. In a PLIIM system having a fixed focal lengthlens and a variable focusing mechanism, the system can adjust to imageobjects under either of these two conditions.

In the PLIIM system of FIG. 1G1, special measures are undertaken toensure that (i) a minimum safe distance is maintained between the VLDsin each PLIM and the user's eyes, and (ii) the planar laser illuminationbeam is prevented from directly scattering into the FOV of the imageformation and detection module, from within the system housing, duringobject illumination and imaging operations. Condition (i) above can beachieved by using a light shield 32A or 32B shown in FIGS. 1G6 and 1G7,respectively, whereas condition (ii) above can be achieved by ensuringthat the planar laser illumination beam from the PLIAs and the field ofview (FOV) of the imaging lens (in the IFD module) do not spatiallyoverlap on any optical surfaces residing within the PLIIM system.Instead, the planar laser illumination beams are permitted to spatiallyoverlap with the FOV of the imaging lens only outside of the systemhousing, measured at a particular point beyond the light transmissionwindow 28, through which the FOV 10 is projected to the exterior of thesystem housing, to perform object imaging operations.

Detailed Description of the Planar Laser Illumination Modules (PLIMS)Employed in the Planar Laser Illumination Arrays (PLIAS) of theIllustrative Embodiments

Referring now to FIGS. 1G8 through 1I2, the construction of each PLIM 14and 15 used in the planar laser illumination arrays (PLIAs) will now bedescribed in greater detail below.

As shown in FIG. 1G8, each planar laser illumination array (PLIA) 6A, 6Bemployed in the PLIIM system of FIG. 1G1, comprises an array of planarlaser illumination modules (PLIMs) 11 mounted on the L-bracket structure32, as described hereinabove. As shown in FIGS. 1G9 through 1G11, eachPLIM of the illustrative embodiment disclosed herein comprises anassembly of subcomponents: a VLD mounting block 14 having a tubulargeometry with a hollow central bore 14A formed entirely therethrough,and a v-shaped notch 14B formed on one end thereof; a visible laserdiode (VLD) 13 (e.g. Mitsubishi ML1XX6 Series high-power 658 nm AlGaInPsemiconductor laser) axially mounted at the end of the VLD mountingblock, opposite the v-shaped notch 14B, so that the laser beam producedfrom the VLD 13 is aligned substantially along the central axis of thecentral bore 14A; a cylindrical lens 16, made of optical glass (e.g.borosilicate) or plastic having the optical characteristics specified,for example, in FIGS. 1G1 and 1G2, and fixedly mounted within theV-shaped notch 14B at the end of the VLD mounting block 14, using anoptical cement or other lens fastening means, so that the central axisof the cylindrical lens 16 is oriented substantially perpendicular tothe optical axis of the central bore 14A; and a focusing lens 15, madeof central glass (e.g. borosilicate) or plastic having the opticalcharacteristics shown, for example, in FIGS. 1H and 1H2, mounted withinthe central bore 14A of the VLD mounting block 14 so that the opticalaxis of the focusing lens 15 is substantially aligned with the centralaxis of the bore 14A, and located at a distance from the VLD whichcauses the laser beam output from the VLD 13 to be converging in thedirection of the cylindrical lens 16. Notably, the function of thecylindrical lens 16 is to disperse (i.e. spread) the focused laser beamfrom focusing lens 15 along the plane in which the cylindrical lens 16has curvature, as shown in FIG. 1I1 while the characteristics of theplanar laser illumination beam (PLIB) in the direction transverse to thepropagation plane are determined by the focal length of the focusinglens 15, as illustrated in FIGS. 1I1 and 1I2.

As will be described in greater detail hereinafter, the focal length ofthe focusing lens 15 within each PLIM hereof is preferably selected sothat the substantially planar laser illumination beam produced from thecylindrical lens 16 is focused at the farthest object distance in thefield of view of the image formation and detection module 3, as shown inFIG. 112, in accordance with the “FBAFOD” principle of the presentinvention. As shown in the exemplary embodiment of FIGS. 1I1 and 1I2,wherein each PLIM has maximum object distance of about 61 inches (i.e.155 centimeters), and the cross-sectional dimension of the planar laserillumination beam emerging from the cylindrical lens 16, in thenon-spreading (height) direction, oriented normal to the propagationplane as defined above, is about 0.15 centimeters and ultimately focuseddown to about 0.06 centimeters at the maximal object distance (i.e. thefarthest distance at which the system is designed to capture images).The behavior of the height dimension of the planar laser illuminationbeam is determined by the focal length of the focusing lens 15 embodiedwithin the PLIM. Proper selection of the focal length of the focusinglens 15 in each PLIM and the distance between the VLD 13 and thefocusing lens 15B indicated by reference No. (D), can be determinedusing the thin lens equation (1) below and the maximum object distancerequired by the PLIIM system, typically specified by the end-user. Aswill be explained in greater detail hereinbelow, this preferred methodof VLD focusing helps compensate for decreases in the power density ofthe incident planar laser illumination beam (on target objects) due tothe fact that the width of the planar laser illumination beam increasesin length for increasing distances away from the imaging subsystem (i.e.object distances).

After specifying the optical components for each PLIM, and completingthe assembly thereof as described above, each PLIM is adjustably mountedto the L bracket position 32A by way of a set of mounting/adjustmentscrews turned through fine-threaded mounting holes formed thereon. InFIG. 1G10, the plurality of PLIMs 11A through 11F are shown adjustablymounted on the L-bracket at positions and angular orientations whichensure substantially uniform power density characteristics in both thenear and far field portions of the planar laser illumination fieldproduced by planar laser illumination arrays (PLIAs) 6A and 6Bcooperating together in accordance with the principles of the presentinvention. Notably, the relative positions of the PLIMs indicated inFIG. 1G9 were determined for a particular set of a commercial VLDs 13used in the illustrative embodiment of the present invention, and, asthe output beam characteristics will vary for each commercial VLD usedin constructing each such PLIM, it is therefore understood that eachsuch PLIM may need to be mounted at different relative positions on theL-bracket of the planar laser illumination array to obtain, from theresulting system, substantially uniform power density characteristics atboth near and far regions of the planar laser illumination fieldproduced thereby.

While a refractive-type cylindrical lens element 16 has been shownmounted at the end of each PLIM of the illustrative embodiments, it isunderstood each cylindrical lens element can be realized usingrefractive, reflective and/or diffractive technology and devices,including reflection and transmission type holographic optical elements(HOEs) well know in the art and described in detail in publishedInternational Application No. WO 99/57579 11/11/99 [108-010PCT000],incorporated herein by reference. The only requirement of the opticalelement mounted at the end of each PLIM is that it has sufficientoptical properties to convert a focusing laser beam transmittedtherethrough, into a laser beam which expands or otherwise spreads outonly along a single plane of propagation, while the laser beam issubstantially unaltered (i.e. neither compressed or expanded) in thedirection normal to the propagation plane. As used hereinafter and inthe claims, the terms “cylindrical lens”, “cylindrical lens element” and“cylindrical optical element (COE)” shall be deemed to embrace all suchalternative embodiments of this aspect of the present invention.

Detailed Description of the Image Formation and Detection ModuleEmployed in the PLIIM System of the First Generalized Embodiment of thePresent Invention

In FIG. 1J1, there is shown a geometrical model (based on the thin lensequation) for the simple imaging subsystem 3B employed in the imageformation and detection module 3 in the PLIIM system of the firstgeneralized embodiment shown in FIG. 1A. As shown in FIG. 11J1, thissimple imaging system 3B consists of a source of illumination (e.g.laser light reflected off a target object) and an imaging lens. Theillumination source is at an object distance r₀ measured from the centerof the imaging lens. In FIG. 1J1, some representative rays of light havebeen traced from the source to the front lens surface. The imaging lensis considered to be of the converging type which, for ordinary operatingconditions, focuses the incident rays from the illumination source toform an image which is located at an image distance r_(i) on theopposite side of the imaging lens. In FIG. 1J1, some representative rayshave also been traced from the back lens surface to the image. Theimaging lens itself is characterized by a focal length f, the definitionof which will be discussed in greater detail hereinbelow.

For the purpose of simplifying the mathematical analysis, the imaginglens is considered to be a thin lens, that is, idealized to a singlesurface with no thickness. The parameters f, r₀ and r_(i), all of whichhave units of length, are related by the “thin lens” equation (1) setforth below:

$\begin{matrix}{\frac{1}{f} = {\frac{1}{r_{0}} + \frac{1}{r_{i}}}} & (1)\end{matrix}$

This equation may be solved for the image distance, which yieldsexpression (2)

$\begin{matrix}{r_{i} = \frac{f\; r_{0}}{r_{0} - f}} & (2)\end{matrix}$

If the object distance r₀ goes to infinity, then expression (2) reducesto r_(i)=f. Thus, the focal length of the imaging lens is the imagedistance at which light incident on the lens from an infinitely distantobject will be focused. Once f is known, the image distance for lightfrom any other object distance can be determined using (2).

Field of View of the Imaging Lens and Resolution of the Detected Image

The basic characteristics of an image detected by the IFD module 3hereof may be determined using the technique of ray tracing, in whichrepresentative rays of light are drawn from the source through theimaging lens and to the image. Such ray tracing is shown in FIG. 1J2. Abasic rule of ray tracing is that a ray from the illumination sourcethat passes through the center of the imaging lens continues undeviatedto the image. That is, a ray that passes through the center of theimaging lens is not refracted. Thus, the size of the field of view (FOV)of the imaging lens may be determined by tracing rays (backwards) fromthe edges of the image detection/sensing array through the center of theimaging lens and out to the image plane as shown in FIG. 1J2, where d isthe dimension of a pixel, n is the number of pixels on the imagedetector array in this direction, and W is the dimension of the field ofview of the imaging lens. Solving for the FOV dimension W, andsubstituting for r_(i) using expression (2) above yields expression (3)as follows:

$\begin{matrix}{W = \frac{d\; {n\left( {r_{0} - f} \right)}}{f}} & (3)\end{matrix}$

Now that the size of the field of view is known, the dpi resolution ofthe image is determined. The dpi resolution of the image is simply thenumber of pixels divided by the dimension of the field of view. Assumingthat all the dimensions of the system are measured in meters, the dotsper inch (dpi) resolution of the image is given by the expression (4) asfollows:

$\begin{matrix}{{d\; p\; i} = \frac{f}{39.37\; {d\left( {r_{0} - f} \right)}}} & (4)\end{matrix}$

Working Distance and Depth of Field of the Imaging Lens

Light returning to the imaging lens that emanates from object surfacesslightly closer to and farther from the imaging lens than objectdistance r₀ will also appear to be in good focus on the image. From apractical standpoint, “good focus” is decided by the decoding software21 used when the image is too blurry to allow the code to be read (i.e.decoded), then the imaging subsystem is said to be “out of focus”. Ifthe object distance r₀ at which the imaging subsystem is ideally focusedis known, then it can be calculated theoretically the closest andfarthest “working distances” of the PLIIM system, given by parametersr_(near) and r_(far), respectively, at which the system will stillfunction. These distance parameters are given by expression (5) and (6)as follows:

$\begin{matrix}{r_{near} = \frac{f\; {r_{0}\left( {f + {D\; F}} \right)}}{f^{2} + {D\; F\; r_{0}}}} & (5)\end{matrix}$

$\begin{matrix}{r_{far} = \frac{f\; {r_{0}\left( {f - {D\; F}} \right)}}{f^{2} - {D\; F\; r_{0}}}} & (6)\end{matrix}$

where D is the diameter of the largest permissible “circle of confusion”on the image detection array. A circle of confusion is essentially theblurred out light that arrives from points at image distances other thanobject distance r₀. When the circle of confusion becomes too large (whenthe blurred light spreads out too much) then one will lose focus. Thevalue of parameter D for a given imaging subsystem is usually estimatedfrom experience during system design, and then determined moreprecisely, if necessary, later through laboratory experiment.

Another optical parameter of interest is the total depth of field Δr,which is the difference between distances r_(far) and r_(near); thisparameter is the total distance over which the imaging system will beable to operate when focused at object distance r₀. This opticalparameter may be expressed by equation (7) below:

$\begin{matrix}{{\Delta \; r} = \frac{2D\; f^{2}F\; {r_{0}\left( {r_{0} - f} \right)}}{f^{4} - {D^{2}F^{2}r_{0}^{2}}}} & (7)\end{matrix}$

It should be noted that the parameter Δr is generally not symmetricabout r₀; the depth of field usually extends farther towards infinityfrom the ideal focal distance than it does back towards the imaginglens.

Modeling a Fixed Focal Length Imaging Subsystem Used in the ImageFormation and Detection Module Of The Present Invention

A typical imaging (i.e. camera) lens used to construct a fixedfocal-length image formation and detection module of the presentinvention might typically consist of three to fifteen or more individualoptical elements contained within a common barrel structure. Theinherent complexity of such an optical module prevents its performancefrom being described very accurately using a “thin lens analysis”,described above by equation (1). However, the results of a thin lensanalysis can be used as a useful guide when choosing an imaging lens fora particular PLIIM system application.

A typical imaging lens can focus light (illumination) originatinganywhere from an infinite distance away, to a few feet away. However,regardless of the origin of such illumination, its rays must be broughtto a sharp focus at exactly the same location (e.g. the film plane orimage detector), which (in an ordinary camera) does not move. At firstglance, this requirement may appear unusual because the thin lensequation (1) above states that the image distance at which light isfocused through a thin lens is a function of the object distance atwhich the light originates, as shown in FIG. 1J3. Thus, it would appearthat the position of the image detector would depend on the distance atwhich the object being imaged is located. An imaging subsystem having avariable focal distance lens assembly avoids this difficulty becauseseveral of its lens elements are capable of movement relative to theothers. For a fixed focal length imaging lens, the leading lenselement(s) can move back and forth a short distance, usuallyaccomplished by the rotation of a helical barrel element which convertsrotational motion into purely linear motion of the lens elements. Thismotion has the effect of changing the image distance to compensate for achange in object distance, allowing the image detector to remain inplace, as shown in the schematic optical diagram of FIG. 1J4.

Modeling a Variable Focal Length (Zoom) Imaging Lens Used in the ImageFormation and Detection Module of the Present Invention

As shown in FIG. 1J5, a variable focal length (zoom) imaging subsystemhas an additional level of internal complexity. A zoom-type imagingsubsystem is capable of changing its focal length over a given range; alonger focal length produces a smaller field of view at a given objectdistance. Consider the case where the PLIIM system needs to illuminateand image a certain object over a range of object distances, butrequires the illuminated object to appear the same size in all acquiredimages. When the object is far away, the PLIIM system will generatecontrol signals that select a long focal length, causing the field ofview to shrink (to compensate for the decrease in apparent size of theobject due to distance). When the object is close, the PLIIM system willgenerate control signals that select a shorter focal length, whichwidens the field of view and preserves the relative size of the object.In many bar code scanning applications, a zoom-type imaging subsystem inthe PLIIM system (as shown in FIGS. 3A through 3J5) ensures that allacquired images of bar code symbols have the same dpi image resolutionregardless of the position of the bar code symbol within the objectdistance of the PLIIM system.

As shown in FIG. 1J5, a zoom-type imaging subsystem has two groups oflens elements which are able to undergo relative motion. The leadinglens elements are moved to achieve focus in the same way as for a fixedfocal length lens. Also, there is a group of lenses in the middle of thebarrel which move back and forth to achieve the zoom, that is, to changethe effective focal length of all the lens elements acting together.

Several Techniques for Accommodating the Field of View (FOV) of a PLIIMSystem to Particular End-User Environments

In many applications, a PLIIM system of the present invention mayinclude an imaging subsystem with a very long focal length imaging lens(assembly), and this PLIIM system must be installed in end-userenvironments having a substantially shorter object distance range,and/or field of view (FOV) requirements or the like. Such problems canexist for PLIIM systems employing either fixed or variable focal lengthimaging subsystems. To accommodate a particular PLIIM system forinstallation in such environments, three different techniquesillustrated in FIGS. 1K1-1K2, 1L1 and 1L2 can be used.

In FIGS. 1K1 and 1K2, the focal length of the imaging lens 3B can befixed and set at the factory to produce a field of view having specifiedgeometrical characteristics for particular applications. In FIG. K1, thefocal length of the image formation and detection module 3 is fixedduring the optical design stage so that the fixed field of view (FOV)thereof substantially matches the scan field width measured at the topof the scan field, and thereafter overshoots the scan field and extendson down to the plane of the conveyor belt 34. In this FOV arrangement,the dpi image resolution will be greater for packages having a higherheight profile above the conveyor belt, and less for envelope-typepackages with low height profiles. In FIG. 1K2, the focal length of theimage formation and detection module 3 is fixed during the opticaldesign stage so that the fixed field of view thereof substantiallymatches the plane slightly above the conveyor belt 34 whereenvelope-type packages are transported. In this FOV arrangement, the dpiimage resolution will be maximized for envelope-type packages which areexpected to be transported along the conveyor belt structure, and thissystem will be unable to read bar codes on packages having aheight-profile exceeding the low-profile scanning field of the system.

In FIG. 1L, a FOV beam folding mirror arrangement is used to fold theoptical path of the imaging subsystem within the interior of the systemhousing so that the FOV emerging from the system housing has geometricalcharacteristics that match the scanning application at hand. As shown,this technique involves mounting a plurality of FOV folding mirrors 9Athrough 9E on the optical bench of the PLIIM system to bounce the FOV ofthe imaging subsystem 3B back and forth before the FOV emerges from thesystem housing. Using this technique, when the FOV emerges from thesystem housing, it will have expanded to a size appropriate for coveringthe entire scan field of the system. This technique is easier topractice with image formation and detection modules having linear imagedetectors, for which the FOV folding mirrors only have to expand in onedirection as the distance from the imaging subsystem increases. In FIG.1L, this direction of FOV expansion occurs in the directionperpendicular to the page. In the case of area-type PLIIM systems, asshown in FIGS. 4A through 6F4, the FOV folding mirrors have toaccommodate a 3-D FOV which expands in two directions. Thus an internalfolding path is easier to arrange for linear-type PLIIM systems.

In FIG. 1L2, the fixed field of view of an imaging subsystem is expandedacross a working space (e.g. conveyor belt structure) by using a motor35 to controllably rotate the FOV 10 during object illumination andimaging operations. When designing a linear-type PLIIM system forindustrial scanning applications, wherein the focal length of theimaging subsystem is fixed, a higher dpi image resolution willoccasionally be required. This implies using a longer focal lengthimaging lens, which produces a narrower FOV and thus higher dpi imageresolution. However, in many applications, the image formation anddetection module in the PLIIM system cannot be physically located farenough away from the conveyor belt (and within the system housing) toenable the narrow FOV to cover the entire scanning field of the system.In this case, a FOV folding mirror 9F can be made to rotate, relative tostationary for folding mirror 9G, in order to sweep the linear FOV fromside to side over the entire width of the conveyor belt, depending onwhere the bar coded package is located. Ideally, this rotating FOVfolding mirror 9F would have only two mirror positions, but this willdepend on how small the FOV is at the top of the scan field. Therotating FOV folding mirror can be driven by motor 35 operated under thecontrol of the system controller 22, as described herein.

Method of Adjusting the Focal Characteristics of the Planar LaserIllumination Beams Generated by Planar Laser Illumination Arrays Used inConjunction with Image Formation and Detection Modules Employing FixedFocal Length Imaging Lenses

In the case of a fixed focal length camera lens, the planar laserillumination beam 7A, 7B is focused at the farthest possible objectdistance in the PLIIM system. In the case of fixed focal length imaginglens, this focus control technique of the present invention is notemployed to compensate for decrease in the power density of thereflected laser beam as a function of 1/r² distance from the imagingsubsystem, but rather to compensate for a decrease in power density ofthe planar laser illumination beam on the target object due to anincrease in object distance away from the imaging subsystem.

It can be shown that laser return light that is reflected by the targetobject (and measured/detected at any arbitrary point in space) decreasesin intensity as the inverse square of the object distance. In the PLIIMsystem of the present invention, the relevant decrease in intensity isnot related to such “inverse square” law decreases, but rather to thefact that the width of the planar laser illumination beam increases asthe object distance increases. This “beam-width/object-distance” lawdecrease in light intensity will be described in greater detail below.

Using a thin lens analysis of the imaging subsystem, it can be shownthat when any form of illumination having a uniform power density E₀(i.e. power per unit area) is directed incident on a target objectsurface and the reflected laser illumination from the illuminated objectis imaged through an imaging lens having a fixed focal length f andf-stop F, the power density E_(pix) (measured at the pixel of the imagedetection array and expressed as a function of the object distance r) isprovided by the expression (8) set forth below:

$\begin{matrix}{E_{pix} = {\frac{E_{0}}{8\; F}\left( {1 - \frac{f}{r}} \right)^{2}}} & (8)\end{matrix}$

FIG. 1M1 shows a plot of pixel power density E_(pix) vs. object distancer calculated using the arbitrary but reasonable values E₀=1 W/m², f=80mm and F=4.5. This plot demonstrates that, in a counter-intuitivemanner, the power density at the pixel (and therefore the power incidenton the pixel, as its area remains constant) actually increases as theobject distance increases. Careful analysis explains this particularoptical phenomenon by the fact that the field of view of each pixel onthe image detection array increases slightly faster with increases inobject distances than would be necessary to compensate for the 1/r²return light losses. A more analytical explanation is provided below.

The width of the planar laser illumination beam increases as objectdistance r increases. At increasing object distances, the constantoutput power from the VLD in each planar laser illumination module(PLIM) is spread out over a longer beam width, and therefore the powerdensity at any point along the laser beam width decreases. To compensatefor this phenomenon, the planar laser illumination beam of the presentinvention is focused at the farthest object distance so that the heightof the planar laser illumination beam becomes smaller as the objectdistance increases; as the height of the planar laser illumination beambecomes narrower towards the farthest object distance, the laser beampower density increases at any point along the width of the planar laserillumination beam. The decrease in laser beam power density due to anincrease in planar laser beam width and the increase in power densitydue to a decrease in planar laser beam height, roughly cancel each otherout, resulting in a power density which either remains approximatelyconstant or increases as a function of increasing object distance, asthe application at hand may require.

When the laser beam is fanned (i.e. spread) out into a substantiallyplanar laser illumination beam by the cylindrical lens element employedwithin each PLIM in the PLIIM system, the total output power in theplanar laser illumination beam is distributed along the width of thebeam in a roughly Gaussian distribution, as shown in the power vs.position plot of FIG. 1M2. Notably, this plot was constructed usingactual data gathered with a planar laser illumination beam focused atthe farthest object distance in the PLIIM system. For comparisonpurposes, the data points and a Gaussian curve fit are shown for theplanar laser beam widths taken at the nearest and farthest objectdistances. To avoid having to consider two dimensions simultaneously(i.e. left-to-right along the planar laser beam width dimension andnear-to-far through the object distance dimension), the discussion belowwill assume that only a single pixel is under consideration, and thatthis pixel views the target object at the center of the planar laserbeam width.

For a fixed focal length imaging lens, the width L of the planar laserbeam is a function of the fan/spread angle θ induced by (i) thecylindrical lens element in the PLIM and (ii) the object distance r, asdefined by the following expression (9):

$\begin{matrix}{{L = {2\; r\; \tan \; \frac{\theta}{2}}}\;} & (9)\end{matrix}$

FIG. 1M3 shows a plot of beam width length L versus object distance rcalculated using θ=50°, demonstrating the planar laser beam widthincreases as a function of increasing object distance.

The height parameter of the planar laser illumination beam “h” iscontrolled by adjusting the focusing lens 15 between the visible laserdiode (VLD) 13 and the cylindrical lens 16, shown in FIGS. 1I1 and 1I2.FIG. 1M4 shows a typical plot of planar laser beam height h vs. imagedistance r for a planar laser illumination beam focused at the farthestobject distance in accordance with the principles of the presentinvention. As shown in FIG. 1M4, the height dimension of the planarlaser beam decreases as a function of increasing object distance.

Assuming a reasonable total laser power output of 20 mW from the VLD 13in each PLIM 11, the values shown in the plots of FIGS. 1M3 and 1M4 canbe used to determine the power density E₀ of the planar laser beam atthe center of its beam width, expressed as a function of objectdistance. This measure, plotted in FIG. 1N, demonstrates that the use ofthe laser beam focusing technique of the present invention, wherein theheight of the planar laser illumination beam is decreased as the objectdistance increases, compensates for the increase in beam width in theplanar laser illumination beam, which occurs for an increase in objectdistance. This yields a laser beam power density on the target objectwhich increases as a function of increasing object distance over asubstantial portion of the object distance range of the PLIIM system.

Finally, the power density E₀ plot shown in FIG. 1N can be used withexpression (1) above to determine the power density on the pixel,E_(pix). This E_(pix) plot is shown in FIG. 1O. For comparison purposes,the plot obtained when using the beam focusing method of the presentinvention is plotted in FIG. 1O against a “reference” power density plotE_(pix) which is obtained when focusing the laser beam at infinity,using a collimating lens (rather than a focusing lens 15) disposed afterthe VLD 13, to produce a collimated-type planar laser illumination beamhaving a constant beam height of 1 mm over the entire portion of theobject distance range of the system. Notably, however, thisnon-preferred beam collimating technique, selected as the reference plotin FIG. 1O, does not compensate for the above-described effectsassociated with an increase in planar laser beam width as a function ofobject distance. Consequently, when using this non-preferred beamfocusing technique, the power density of the planar laser illuminationbeam produced by each PLIM decreases as a function of increasing objectdistance.

Therefore, in summary, where a fixed or variable focal length imagingsubsystem is employed in the PLIIM system hereof, the planar laser beamfocusing technique of the present invention described above helpscompensate for decreases in the power density of the incident planarillumination beam due to the fact that the width of the planar laserillumination beam increases for increasing object distances away fromthe imaging subsystem.

Producing a Composite Planar Laser Illumination Beam HavingSubstantially Uniform Power Density Characteristics in Near and FarFields, by Additively Combining the Individual Gaussian Power DensityDistributions of Planar Laser Illumination Beams Produced by PlanarLaser Illumination Beam Modules (PLIMS) in Planar Laser IlluminationArrays (PLIAS)

Having described the best known method of focusing the planar laserillumination beam produced by each VLD in each PLIM in the PLIIM systemhereof, it is appropriate at this juncture to describe how theindividual Gaussian power density distributions of the planar laserillumination beams produced a PLIA 6A, 6B are additively combined toproduce a composite planar laser illumination beam having substantiallyuniform power density characteristics in near and far fields, asillustrated in FIGS. 1P1 and 1P2.

When the laser beam produced from the VLD is transmitted through thecylindrical lens, the output beam will be spread out into a laserillumination beam extending in a plane along the direction in which thelens has curvature. The beam size along the axis which corresponds tothe height of the cylindrical lens will be transmitted unchanged. Whenthe planar laser illumination beam is projected onto a target surface,its profile of power versus displacement will have an approximatelyGaussian distribution. In accordance with the principles of the presentinvention, the plurality of VLDs on each side of the IFD module arespaced out and tilted in such a way that their individual power densitydistributions add up to produce a (composite) planar laser illuminationbeam having a magnitude of illumination which is distributedsubstantially uniformly over the entire working depth of the PLIIMsystem (i.e. along the height and width of the composite planar laserillumination beam).

The actual positions of the PLIMs along each planar laser illuminationarray are indicated in FIG. 1G3 for the exemplary PLIIM system shown inFIGS. 1G1 through 1I2. The mathematical analysis used to analyze theresults of summing up the individual power density functions of thePLIMs at both near and far working distances was carried out using theMatlab™ mathematical modeling program by Mathworks, Inc.(http://www.mathworks.com). These results are set forth in the dataplots of FIGS. 1P1 and 1P2. Notably, in these data plots, the totalpower density is greater at the far field of the working range of thePLIIM system. This is because the VLDs in the PLIMs are focused toachieve minimum beam width thickness at the farthest object distance ofthe system, whereas the beam height is somewhat greater at the nearfield region. Thus, although the far field receives less illuminationpower at any given location, this power is concentrated into a smallerarea, which results in a greater power density within the substantiallyplanar extent of the planar laser illumination beam of the presentinvention.

When aligning the individual planar laser illumination beams (i.e.planar beam components) produced from each PLIM, it will be important toensure that each such planar laser illumination beam spatially coincideswith a section of the FOV of the imaging subsystem, so that thecomposite planar laser illumination beam produced by the individual beamcomponents spatially coincides with the FOV of the imaging subsystemthroughout the entire working depth of the PLIIM system.

Second Alternative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

In FIG. 1Q1, the second illustrative embodiment of the PLIIM system ofFIG. 1A is shown comprising: a 1-D type image formation and detection(IFD) module 3′, as shown in FIG. 1B1; and a pair of planar laserillumination arrays 6A and 6B. As shown, these arrays 6A and 6B arearranged in relation to the image formation and detection module 3 sothat the field of view thereof is oriented in a direction that iscoplanar with the planes of laser illumination produced by the planarillumination arrays, without using any laser beam or field of viewfolding mirrors. One primary advantage of this system architecture isthat it does not require any laser beam or FOV folding mirrors, employsthe few optical surfaces, and maximizes the return of laser light, andis easy to align. However, it is expected that this system design willmost likely require a system housing having a height dimension which isgreater than the height dimension required by the system design shown inFIG. 1B1.

As shown in FIG. 1Q2, PLIIM system 1B shown in FIG. 1Q1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3 having an imaging subsystem witha fixed focal length imaging lens, a fixed focal distance, and a fixedfield of view, and 1-D image detection array (e.g. Piranha Model Nos.CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, from Dalsa, Inc.USA—http:/www/dalsa.com) for detecting 1-D line images formed thereon bythe imaging subsystem; an image frame grabber 19 operably connected tothe linear-type image formation and detection module 3, for accessing1-D images (i.e. 1-D digital image data sets) therefrom and building a2-D digital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner. Preferably, the PLIIM system of FIGS.1O1 and 102 is realized using the same or similar constructiontechniques shown in FIGS. 1G1 through 1I2, and described above.

Third Alternative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

In FIG. 1R1, the third illustrative embodiment of the PLIIM system ofFIGS. 1A, 1C are shown comprising: a 1-D type image formation anddetection (IFD) module 3 having a field of view (FOV), as shown in FIG.1B1; a pair of planar laser illumination arrays 6A and 6B for producingfirst and second planar laser illumination beams; and a pair of planarlaser beam folding mirrors 37A and 37B arranged. The function of theplanar laser illumination beam folding mirrors 37A and 37B is to foldthe optical paths of the first and second planar laser illuminationbeams produced by the pair of planar illumination arrays 37A and 37Bsuch that the field of view (FOV) of the image formation and detectionmodule 3 is aligned in a direction that is coplanar with the planes offirst and second planar laser illumination beams during objectillumination and imaging operations. One notable disadvantage of thissystem architecture is that it requires additional optical surfaceswhich can reduce the intensity of outgoing laser illumination andtherefore reduce slightly the intensity of returned laser illuminationreflected off target objects. Also this system design requires a morecomplicated beam/FOV adjustment scheme, than not using any planar laserillumination beam folding mirrors. This system design can be best usedwhen the planar laser illumination beams do not have large apex anglesto provide sufficiently uniform illumination. In this system embodiment,the PLIMs are mounted on the optical bench as far back as possible fromthe beam folding mirrors, and cylindrical lenses with larger radiuseswill be employed in the design of each PLIM.

As shown in FIG. 1R2, PLIIM system 1C shown in FIG. 1R1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 6A through 6B, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module having an imaging subsystem with afixed focal length imaging lens, a fixed focal distance, and a fixedfield of view, and 1-D image detection array (e.g. Piranha Model Nos.CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, from Dalsa, Inc.USA—http:/www/dalsa.com) for detecting 1-D line images formed thereon bythe imaging subsystem; pair of planar laser beam folding mirrors 37A and37B arranged so as to fold the optical paths of the first and secondplanar laser illumination beams produced by the pair of planarillumination arrays 6A and 6B; an image frame grabber 19 operablyconnected to the linear-type image formation and detection module 3, foraccessing 1-D images (i.e. 1-D digital image data sets) therefrom andbuilding a 2-D digital image of the object being illuminated by theplanar laser illumination arrays 6A and 6B; an image data buffer (e.g.VRAM) 20 for buffering 2-D images received from the image frame grabber19; a decode image processor 21, operably connected to the image databuffer 20, for carrying out image processing algorithms (including barcode symbol decoding algorithms) and operators on digital images storedwithin the image data buffer; and a system controller 22 operablyconnected to the various components within the system for controllingthe operation thereof in an orchestrated manner. Preferably, the PLIIMsystem of FIGS. 1Q1 and 1Q2 is realized using the same or similarconstruction techniques shown in FIGS. 1G1 through 1I2, and describedabove.

Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 1A

In FIG. 1S1, the fourth illustrative embodiment of the PLIIM system ofFIGS. 1A, indicated by reference No. 1D is shown comprising: a 1-D typeimage formation and detection (IFD) module 3 having a field of view(FOV), as shown in FIG. 1B1; a pair of planar laser illumination arrays6A and 6B for producing first and second planar laser illuminationbeams; a field of view folding mirror 9 for folding the field of view(FOV) of the image formation and detection module 3 about 90 degreesdownwardly; and a pair of planar laser beam folding mirrors 37A and 37Barranged so as to fold the optical paths of the first and second planarlaser illumination beams produced by the pair of planar illuminationarrays 6A and 6B such that the planes of first and second planar laserillumination beams 7A and 7B are in a direction that is coplanar withthe field of view of the image formation and detection module 3. Despiteinheriting most of the disadvantages associated with the system designsshown in FIGS. 1B1 and 1R1, this system architecture allows the lengthof the system housing to be easily minimized, at the expense of anincrease in the height and width dimensions of the system housing.

As shown in FIG. 1S2, PLIIM system 1D shown in FIG. 1S1 comprises:planar laser illumination arrays 6A and 6B, each having a plurality ofplanar laser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3 having an imaging subsystem witha fixed focal length imaging lens, a fixed focal distance, and a fixedfield of view, and 1-D image detection array (e.g. Piranha Model Nos.CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, from Dalsa, Inc.USA—http:/www/dalsa.com) for detecting 1-D line images formed thereon bythe imaging subsystem; a field of view folding mirror 9 for folding thefield of view (FOV) of the image formation and detection module 3; apair of planar laser beam folding mirrors 9 and 3 arranged so as to foldthe optical paths of the first and second planar laser illuminationbeams produced by the pair of planar illumination arrays 37A and 37B; animage frame grabber 19 operably connected to the linear-type imageformation and detection module 3, for accessing 1-D images (i.e. 1-Ddigital image data sets) therefrom and building a 2-D digital image ofthe object being illuminated by the planar laser illumination arrays 6Aand 6B; an image data buffer (e.g. VRAM) 20 for buffering 2-D imagesreceived from the image frame grabber 19; a decode image processor 21,operably connected to the image data buffer 20, for carrying out imageprocessing algorithms (including bar code symbol decoding algorithms)and operators on digital images stored within the image data buffer; anda system controller 22 operably connected to the various componentswithin the system for controlling the operation thereof in anorchestrated manner. Preferably, the PLIIM system of FIGS. 1S1 and 1S2is realized using the same or similar construction techniques shown inFIGS. 1G1 through 1I2, and described above.

Applications for the First Generalized Embodiment of the PLIIM System ofthe Present Invention, And the Illustrative Embodiments Thereof

Fixed focal distance PLIIM systems shown in FIGS. 1B1 through 1U areideal for applications in which there is little variation in the objectdistance, such as in a conveyor-type bottom scanner application. As suchscanning systems employ a fixed focal length imaging lens, the imageresolution requirements of such applications must be examined carefullyto determine that the image resolution obtained is suitable for theintended application. Because the object distance is approximatelyconstant for a bottom scanner application (i.e. the bar code almostalways is illuminated and imaged within the same object plane), the dpiresolution of acquired images will be approximately constant. As imageresolution is not a concern in this type of scanning applications,variable focal length (zoom) control is unnecessary, and a fixed focallength imaging lens should suffice and enable good results.

A fixed focal distance PLIIM system generally takes up less space than avariable or dynamic focus model because more advanced focusing methodsrequire more complicated optics and electronics, and additionalcomponents such as motors. For this reason, fixed focus PLIIM systemsare good choices for handheld and presentation scanners as indicated inFIG. 1U, wherein space and weight are always critical characteristics.In these applications, however, the object distance can vary over arange from several to a twelve or

more inches, and so the designer must exercise care to ensure that thescanner's depth of field (DOF) alone will be sufficient to accommodateall possible variations in target object distance and orientation. Also,because a fixed focus imaging subsystem implies a fixed focal lengthcamera lens, the variation in object distance implies that the dots perinch resolution of the image will vary as well. The focal length of theimaging lens must be chosen so that the angular width of the field ofview (FOV) is narrow enough that the dpi image resolution will not fallbelow the minimum acceptable value anywhere within the range of objectdistances supported by the PLIIM system.

Second Generalized Embodiment of the Planar Laser Illumination andElectronic Imaging System of the Present Invention

The second generalized embodiment of the PLIIM system of the presentinvention 11 is illustrated in FIGS. 1V1 and 1V2. As shown in FIG. 1V1,the PLIIM system 1′ comprises: a housing 2 of compact construction; alinear (i.e. 1-dimensional) type image formation and detection (IFD)module 3′; and a pair of planar laser illumination arrays (PLIAs) 6A and6B mounted on opposite sides of the IFD module 3′. During systemoperation, laser illumination arrays 6A and 6B each produce a movingplane of laser illumination beam 12′ which synchronously moves and isdisposed substantially coplanar with the field of view (FOV) of theimage formation and detection module 3′, so as to scan a bar code symbolor other graphical structure 4 disposed stationary within a 3-D scanningregion.

As shown in FIGS. 2V2 and 2V3, the PLIIM system of FIG. 2V1 comprises:an image formation and detection module 3′ having an imaging subsystem3B′ with a fixed focal length imaging lens, a fixed focal distance, anda fixed field of view, and a 1-D image detection array 3 (e.g. PiranhaModel Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, from Dalsa,Inc. USA—http:/www/dalsa.com) for detecting 1-D line images formedthereon by the imaging subsystem; a field of view sweeping mirror 9operably connected to a motor mechanism 38 under control of systemcontroller 22, for folding and sweeping the field of view of the imageformation and detection module 3; a pair of planar laser illuminationarrays 6A and 6B for producing planar laser illumination beams 7A and7B; a pair of planar laser illumination beam folding/sweeping mirrors37A and 37B operably connected to motor mechanisms 39A and 39B,respectively, under control of system controller 22, for folding andsweeping the planar laser illumination beams 7A and 7B, respectively, insynchronism with the FOV being swept by the FOV folding and sweepingmirror 9; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

An image formation and detection (IFD) module 3 having an imaging lenswith a fixed focal length has a constant angular field of view (FOV);that is, the farther the target object is located from the IFD module,the larger the projection dimensions of the imaging subsystem's FOVbecome on the surface of the target object. A disadvantage to this typeof imaging lens is that the resolution of the image that is acquired, interms of pixels or dots per inch, varies as a function of the distancefrom the target object to the imaging lens. However, a fixed focallength imaging lens is easier and less expensive to design and producethan the alternative, a zoom-type imaging lens which will be discussedin detail hereinbelow with reference to FIGS. 3A through 3J4.

Each planar laser illumination module 6A through 6B in PLIIM system 1′is driven by a VLD driver circuit 18 under the system controller 22.Notably, laser illumination beam folding/sweeping mirror 37A′ and 38B′,and FOV folding/sweeping mirror 9′ are each rotatably driven by amotor-driven mechanism 38, 39A, and 39B, respectively, operated underthe control of the system controller 22. These three mirror elements canbe synchronously moved in a number of different ways. For example, themirrors 37A′, 37B′ and 9′ can be jointly rotated together under thecontrol of one or more motor-driven mechanisms, or each mirror elementcan be driven by a separate driven motor which is synchronouslycontrolled to enable the planar laser illumination beams 7A, 7B and FOV10 to move together in a spatially-coplanar manner during illuminationand detection operations within the PLIIM system.

In accordance with the present invention, the planar laser illuminationarrays 6A and 6B, the linear image formation and detection module 3, thefolding/sweeping FOV mirror 9′, and the planar laser illumination beamfolding/sweeping mirrors 37A′ and 37B′ employed in this generalizedsystem embodiment, are fixedly mounted on an optical bench or chassis 8so as to prevent any relative motion (which might be caused by vibrationor temperature changes) between: (i) the image forming optics (e.g.imaging lens) within the image formation and detection module 3 and theFOV folding/sweeping mirror 9′ employed therewith; and (ii) each planarlaser illumination module (i.e. VLD/cylindrical lens assembly) and theplanar laser illumination beam folding/sweeping mirrors 37A′ and 37B′employed in this PLIIM system configuration. Preferably, the chassisassembly should provide for easy and secure alignment of all opticalcomponents employed in the planar laser illumination arrays 6A′ and 6B′,beam folding/sweeping mirrors 37A′ and 37B′, the image formation anddetection module 3 and FOV folding/sweeping mirror 9′, as well as beeasy to manufacture, service and repair. Also, this generalized PLIIMsystem embodiment 1′ employs the general “planar laser illumination” and“focus beam at farthest object distance (FBAFOD)” principles describedabove.

Applications for the Second Generalized Embodiment of the PLIIM Systemof the Present Invention

The fixed focal length PLIIM system shown in FIGS. 1V1-1V3 has a 3-Dfixed field of view which, while spatially-aligned with a compositeplanar laser illumination beam 12 in a coplanar manner, is automaticallyswept over a 3-D scanning region within which bar code symbols and othergraphical indicia 4 may be illuminated and imaged in accordance with theprinciples of the present invention. As such, this generalizedembodiment of the present invention is ideally suited for use inhand-supportable and hands-free presentation type bar code symbolreaders shown in FIGS. 1V4 and 1V5, respectively, in whichrasterlike-scanning (i.e. up and down) patterns can be used for reading1-D as well as 2-D bar code symbologies such as the PDF 147 symbology.In general, the PLIM system of this generalized embodiment may have anyof the housing form factors disclosed and described in Applicant'scopending U.S. application Ser. Nos. 09/204,176 entitled filed Dec. 3,1998 and 09/452,976 filed Dec. 2, 1999, and WIPO Publication No. WO00/33239 published Jun. 8, 2000, incorporated herein by reference. Thebeam sweeping technology disclosed in copending application Ser. No.08/931,691 filed Sep. 16, 1997, incorporated herein by reference, can beused to uniformly sweep both the planar laser illumination beam andlinear FOV in a coplanar manner during illumination and imagingoperations.

Third Generalized Embodiment of the PLIIM System of the PresentInvention

The third generalized embodiment of the PLIIM system of the presentinvention 40 is illustrated in FIG. 2A. As shown therein, the PLIIMsystem 40 comprises: a housing 2 of compact construction; a linear (i.e.1-dimensional) type image formation and detection (IFD) module 3′including a 1-D electronic image detection array 3A, a linear (1-D)imaging subsystem (LIS) 3B′ having a fixed focal length, a variablefocal distance, and a fixed field of view (FOV), for forming a 1-D imageof an illuminated object located within the fixed focal distance and FOVthereof and projected onto the 1-D image detection array 3A, so that the1-D image detection array 3A can electronically detect the image formedthereon and automatically produce a digital image data set 5representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 3′, such that each planarlaser illumination array 6A and 6B produces a composite plane of laserbeam illumination 12 which is disposed substantially coplanar with thefield view of the image formation and detection module 3′ during objectillumination and image detection operations carried out by the PLIIMsystem.

In accordance with the present invention, the planar laser illuminationarrays 6A and 6B, the linear image formation and detection module 3′,and any non-moving FOV and/or planar laser illumination beam foldingmirrors employed in any configuration of this generalized systemembodiment, are fixedly mounted on an optical bench or chassis so as toprevent any relative motion (which might be caused by vibration ortemperature changes) between: (i) the image forming optics (e.g. imaginglens) within the image formation and detection module 3′ and anystationary FOV folding mirrors employed therewith; and (ii) each planarlaser illumination module (i.e. VLD/cylindrical lens assembly) and anyplanar laser illumination beam folding mirrors employed in the PLIIMsystem configuration. Preferably, the chassis assembly should providefor easy and secure alignment of all optical components employed in theplanar laser illumination arrays 6A and 6B as well as the imageformation and detection module 3′, as well as be easy to manufacture,service and repair. Also, this generalized PLIIM system embodiment 40employs the general “planar laser illumination” and “focus beam atfarthest object distance (FBAFOD)” principles described above. Variousillustrative embodiments of this generalized PLIIM system will bedescribed below.

An image formation and detection (IFD) module 3 having an imaging lenswith variable focal distance, as employed in the PLIIM system of FIG.2A, can adjust its image distance to compensate for a change in thetarget's object distance; thus, at least some of the component lenselements in the imaging subsystem are movable, and the depth of field ofthe imaging subsystems does not limit the ability of the imagingsubsystem to accommodate possible object distances and orientations. Avariable focus imaging subsystem is able to move its components in sucha way as to change the image distance of the imaging lens to compensatefor a change in the target's object distance, thus preserving good focusno matter where the target object might be located. Variable focus canbe accomplished in several ways, namely: by moving lens elements; movingimager detector/sensor; and dynamic focus. Each of these differentmethods will be summarized below for sake of convenience.

Use of Moving Lens Elements in the Image Formation and Detection Module

The imaging subsystem in this generalized PLIIM system embodiment canemploy an imaging lens which is made up of several component lensescontained in a common lens barrel. A variable focus type imaging lenssuch as this can move one or more of its lens elements in order tochange the effective distance between the lens and the image sensor,which remains stationary. This change in the image distance compensatesfor a change in the object distance of the target object and keeps thereturn light in focus. The position at which the focusing lenselement(s) must be in order to image light returning from a targetobject at a given object distance is determined by consulting a lookuptable, which must be constructed ahead of time, either experimentally orby design software, well known in the optics art.

Use of an Moving Image Detection Array in the Image Formation andDetection Module

The imaging subsystem in this generalized PLIIM system embodiment can beconstructed so that all the lens elements remain stationary, with theimaging detector/sensor array being movable relative to the imaging lensso as to change the image distance of the imaging subsystem. Theposition at which the image detector/sensor must be located to imagelight returning from a target at a given object distance is determinedby consulting a lookup table, which must be constructed ahead of time,either experimentally or by design software, well known in the art.

Use of Dynamic Focal Distance Control in the Image Formation andDetection Module

The imaging subsystem in this generalized PLIIM system embodiment can bedesigned to embody a “dynamic” form of variable focal distance (i.e.focus) control, which is an advanced form of variable focus control. Inconventional variable focus control schemes, one focus (i.e. focaldistance) setting is established in anticipation of a given targetobject. The object is imaged using that setting, then another setting isselected for the next object image, if necessary. However, depending onthe shape and orientation of the target object, a single target objectmay exhibit enough variation in its distance from the imaging lens tomake it impossible for a single focus setting to acquire a sharp imageof the entire object. In this case, the imaging subsystem must changeits focus setting while the object is being imaged. This adjustment doesnot have to be made continuously; rather, a few discrete focus settingswill generally be sufficient. The exact number will depend on the shapeand orientation of the package being imaged and the depth of field ofthe imaging subsystem used in the IFD module.

It should be noted that dynamic focus control is only used with a linearimage detection/sensor array, as used in the system embodiments shown inFIGS. 2A through 3J4. The reason for this limitation is quite clear: anarea-type image detection array captures an entire image after a rapidnumber of exposures to the planar laser illumination beam, and althoughchanging the focus setting of the imaging subsystem might clear up theimage in one part of the detector array, it would induce blurring inanother region of the image, thus failing to improve the overall qualityof the acquired image.

First Illustrative Embodiment of the PLIIM System Shown in FIG. 2A

The first illustrative embodiment of the PLIIM system of FIG. 2A 40A isshown in FIG. 2B1. As illustrated therein, the field of view of theimage formation and detection module 3′ and the first and second planarlaser illumination beams 7A and 7B produced by the planar illuminationarrays 6A and 6B, respectively, are arranged in a substantially coplanarrelationship during object illumination and image detection operations.

The PLIIM system illustrated in FIG. 2B1 is shown in greater detail inFIG. 2B2. As shown therein, the linear image formation and detectionmodule 3′ is shown comprising an imaging subsystem 3B′, and a lineararray of photo-electronic detectors 3A realized using CCD technology(e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D lineimages (e.g. 6000 pixels, @ 60 MHZ scanning rate) formed thereon by theimaging subsystem 3B′, providing an image resolution of 200 dpi or 8pixels/mm, as the image resolution that results from a fixed focallength imaging lens is the function of the object distance (i.e. thelonger the object distance, the lower the resolution). The imagingsubsystem 3B′ has a fixed focal length imaging lens (e.g. 80 mm Pentaxlens, F4.5), a fixed field of view (FOV), and a variable focal distanceimaging capability (e.g. 36′ total scanning range), and an auto-focusingimage plane with a response time of about 20-30 milliseconds over about5 mm working range.

As shown, each planar laser illumination array (PLIA) 6A, 6B comprises aplurality of planar laser illumination modules (PLIMs) 11A through 11F,closely arranged relative to each other, in a rectilinear fashion. Astaught hereinabove, the relative spacing and orientation of each PLIM 11is such that the spatial intensity distribution of the individual planarlaser beams 7A, 7B superimpose and additively produce composite planarlaser illumination beam 12 having a substantially uniform power densitydistribution along the widthwise dimensions of the laser illuminationbeam, throughout the entire working range of the PLIIM system.

As shown in FIG. 2C1, the PLIIM system of FIG. 2B1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3A, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

FIG. 2C2 illustrates in greater detail the structure of the IFD module3′ used in the PLIIM system of FIG. 2B1. As shown, the IFD module 3′comprises a variable focus fixed focal length imaging subsystem 3B′ anda 1-D image detecting array 3A mounted along an optical bench 30contained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3B′ mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis with an optical element translator 3C in response to afirst set of control signals 3E generated by the system controller 22,while the entire group of focal lens elements remain stationary.Alternatively, focal distance control can also be provided by moving theentire group of focal lens elements back and forth with translator 3C inresponse to a first set of control signals 3E generated by the systemcontroller, while the 1-D image detecting array 3A remains stationary.In customized applications, it is possible for the individual lenselements in the group of focusing lens elements 3B′ to be moved inresponse to control signals generated by the system controller 22.Regardless of the approach taken, an IFD module 3′ with variable focusfixed focal length imaging can be realized in a variety of ways, eachbeing embraced by the spirit of the present invention.

Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

The second illustrative embodiment of the PLIIM system of FIG. 2A 40B isshown in FIG. 2D1 comprising: an image formation and detection module 3′having an imaging subsystem 3B′ with a fixed focal length imaging lens,a variable focal distance and a fixed field of view, and a linear arrayof photo-electronic detectors 3A realized using CCD technology (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem 3B′; a field of view foldingmirror 9 for folding the field of view of the image formation anddetection module 3′; and a pair of planar laser illumination arrays 6Aand 6B arranged in relation to the image formation and detection module3′ such that the field of view thereof folded by the field of viewfolding mirror 9 is oriented in a direction that is coplanar with thecomposite plane of laser illumination 12 produced by the planarillumination arrays, during object illumination and image detectionoperations, without using any laser beam folding mirrors.

One primary advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to be installed within a compartment (or cavity) of a housinghaving relatively low height dimensions. Also, in this system design,there is a relatively high degree of freedom provided in where the imageformation and detection module 3′ can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to be practiced in a relatively easy manner.

As shown in FIG. 2D2, the PLIIM system of FIG. 2D1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3′, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

FIG. 2D2 illustrates in greater detail the structure of the IFD module3′ used in the PLIIM system of FIG. 2D1. As shown, the IFD module 3′comprises a variable focus fixed focal length imaging subsystem 3B′ anda 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A′ mounted along theoptical bench before the image detecting array 3A′, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis with a translator 3E in response to a first set ofcontrol signals 3E generated by the system controller 22, while theentire group of focal lens elements remain stationary. Alternatively,focal distance control can also be provided by moving the entire groupof focal lens elements 3B′ back and forth with translator 3C in responseto a first set of control signals 3E generated by the system controller22, while the 1-D image detecting array 3A remains stationary. Incustomized applications, it is possible for the individual lens elementsin the group of focusing lens elements 3B′ to be moved in response tocontrol signals generated by the system controller. Regardless of theapproach taken, an IFD module 3′ with variable focus fixed focal lengthimaging can be realized in a variety of ways, each being embraced by thespirit of the present invention.

Third Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

The second illustrative embodiment of the PLIIM system of FIG. 2A 40C isshown in FIG. 2D1 comprising: an image formation and detection module 3′having an imaging subsystem 3B′ with a fixed focal length imaging lens,a variable focal distance and a fixed field of view, and a linear arrayof photo-electronic detectors 3A realized using CCD technology (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem 3B′; a pair of planar laserillumination arrays 6A and 6B for producing first and second planarlaser illumination beams 7A, 7B, and a pair of planar laser beam foldingmirrors 37A and 37B for folding the planes of the planar laserillumination beams produced by the pair of planar illumination arrays 6Aand 6B, in a direction that is coplanar with the plane of the field ofview of the image formation and detection during object illumination andimage detection operations.

The primary disadvantage of this system architecture is that it requiresadditional optical surfaces (i.e. the planar laser beam folding mirrors)which reduce outgoing laser light and therefore the return laser lightslightly. Also this embodiment requires a complicated beam/FOVadjustment scheme. Thus, this system design can be best used when theplanar laser illumination beams do not have large apex angles to providesufficiently uniform illumination. Notably, in this system embodiment,the PLIMs are mounted on the optical bench 8 as far back as possiblefrom the beam folding mirrors 37A, 37B, and cylindrical lenses 16 withlarger radiuses will be employed in the design of each PLIM 11.

As shown in FIG. 2E2, the PLIIM system of FIG. 2E1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3A, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

FIG. 2E3 illustrates in greater detail the structure of the IFD module3′ used in the PLIIM system of FIG. 2E1. As shown, the IFD module 3′comprises a variable focus fixed focal length imaging subsystem 3B′ anda 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis in response to a first set of control signals 3Egenerated by the system controller 22, while the entire group of focallens elements 3B′ remain stationary. Alternatively, focal distancecontrol can also be provided by moving the entire group of focal lenselements 3B′ back and forth with translator 3C in response to a firstset of control signals 3E generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. In customizedapplications, it is possible for the individual lens elements in thegroup of focusing lens elements 3B′ to be moved in response to controlsignals generated by the system controller 22. Regardless of theapproach taken, an IFD module 3′ with variable focus fixed focal lengthimaging can be realized in a variety of ways, each being embraced by thespirit of the present invention.

Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 2A

The fourth illustrative embodiment of the PLIIM system of FIG. 2A 40D isshown in FIG. 2F1 comprising: an image formation and detection module 3′having an imaging subsystem 3B′ with a fixed focal length imaging lens,a variable focal distance and a fixed field of view, and a linear arrayof photo-electronic detectors 3A realized using CCD technology (e.g.Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D line imagesformed thereon by the imaging subsystem 3B′; a field of view foldingmirror 9 for folding the FOV of the imaging subsystem 3B′; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams; and a pair of planar laser beamfolding mirrors 37A and 37B arranged in relation to the planar laserillumination arrays 6A and 6B so as to fold the optical paths of thefirst and second planar laser illumination beams 7A, 7B in a directionthat is coplanar with the folded FOV of the image formation anddetection module 3′, during object illumination and image detectionoperations.

As shown in FIG. 2F2, the PLIIM system 40D of FIG. 2F1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11B, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3′; a field of view folding mirror9 for folding the field of view of the image formation and detectionmodule 3′; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3A, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

FIG. 2F3 illustrates in greater detail the structure of the IFD module3′ used in the PLIIM system of FIG. 2F1. As shown, the IFD module 3′comprises a variable focus fixed focal length imaging subsystem 3B′ anda 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench 3D before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis with translator 3C in response to a first set ofcontrol signals 3E generated by the system controller 22, while theentire group of focal lens elements 3B′ remain stationary.Alternatively, focal distance control can also be provided by moving theentire group of focal lens elements 3B′ back and forth with translator3C in response to a first set of control signals 3E generated by thesystem controller 22, while the 1-D image detecting array 3A remainsstationary. In customized applications, it is possible for theindividual lens elements in the group of focusing lens elements 3B′ tobe moved in response to control signals generated by the systemcontroller 22. Regardless of the approach taken, an IFD module withvariable focus fixed focal length imaging can be realized in a varietyof ways, each being embraced by the spirit of the present invention.

Applications for the Third Generalized Embodiment of the PLIIM System ofthe Present Invention, and the Illustrative Embodiments Thereof

As the PLIIM systems shown in FIGS. 2A through 2F3 employ an IFD module3′ having a linear image detecting array and an imaging subsystem havingvariable focus (i.e. focal distance) control, such PLIIM systems aregood candidates for use in a conveyor top scanner application, as shownin FIGS. 2G, as the variation in target object distance can be up to ameter or more (from the imaging subsystem). In general, such objectdistances are too great a range for the depth of field (DOF)characteristics of the imaging subsystem alone to accommodate suchobject distance parameter variations during object illumination andimaging operations. Provision for variable focal distance control isgenerally sufficient for the conveyor top scanner application shown inFIG. 2G, as the demands on the depth of field and variable focus ordynamic focus control characteristics of such PLIIM system are not assevere in the conveyor top scanner application, as they might be in theconveyor side scanner application, also illustrated in FIG. 2G.

Notably, by adding dynamic focusing functionality to the imagingsubsystem of any of the embodiments shown in FIGS. 2A through 2F3, theresulting PLIIM system becomes appropriate for the conveyorside-scanning application discussed above, where the demands on thedepth of field and variable focus or dynamic focus requirements aregreater compared to a conveyor top scanner application.

Fourth Generalized Embodiment of the PLIIM System of the PresentInvention

The fourth generalized embodiment of the PLIIM system 40′ of the presentinvention is illustrated in FIGS. 2I1 and 2I2. As shown in FIG. 2I1, thePLIIM system 40′ comprises: a housing 2 of compact construction; alinear (i.e. 1-dimensional) type image formation and detection (IFD)module 3′; and a pair of planar laser illumination arrays (PLIAs) 6A and6B mounted on opposite sides of the IFD module 3′. During systemoperation, laser illumination arrays 6A and 6B each produce a movingplanar laser illumination beam 12′ which synchronously moves and isdisposed substantially coplanar with the field of view (FOV) of theimage formation and detection module 3′, so as to scan a bar code symbolor other graphical structure 4 disposed stationary within a 3-D scanningregion.

As shown in FIGS. 2I2 and 2I3, the PLIIM system of FIG. 2I1 comprises:an image formation and detection module 3′ having an imaging subsystem3B′ with a fixed focal length imaging lens, a variable focal distanceand a fixed field of view, and a linear array of photo-electronicdetectors 3A realized using CCD technology (e.g. Piranha Model Nos.CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, from Dalsa, Inc.USA—http:/www/dalsa.com) for detecting 1-D line images formed thereon bythe imaging subsystem 3B′; a field of view folding and sweeping mirror9′ for folding and sweeping the field of view 10 of the image formationand detection module 3′; a pair of planar laser illumination arrays 6Aand 6B for producing planar laser illumination beams 7A and 7B; a pairof planar laser illumination beam sweeping mirrors 37A′ and 37B′ forfolding and sweeping the planar laser illumination beams 7A and 7B,respectively, in synchronism with the FOV being swept by the FOV foldingand sweeping mirror 9′; an image frame grabber 19 operably connected tothe linear-type image formation and detection module 3A, for accessing1-D images (i.e. 1-D digital image data sets) therefrom and building a2-D digital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner. As shown in FIG. 2F2, each planarlaser illumination module 11A through 11F, is driven by a VLD drivercircuit 18 under the system controller 22. Notably, laser illuminationbeam folding/sweeping mirrors 37A′ and 37B′, and FOV folding/sweepingmirror 9′ are each rotatably driven by a motor-driven mechanism 39A,39B, 38, respectively, operated under the control of the systemcontroller 22. These three mirror elements can be synchronously moved ina number of different ways. For example, the mirrors 37A′, 37B′ and 9′can be jointly rotated together under the control of one or moremotor-driven mechanisms, or each mirror element can be driven by aseparate driven motor which are synchronously controlled to enable thecomposite planar laser illumination beam and FOV to move together in aspatially-coplanar manner during illumination and detection operationswithin the PLIIM system.

FIG. 2I4 illustrates in greater detail the structure of the IFD module3′ used in the PLIIM system of FIG. 2I1. As shown, the IFD module 3′comprises a variable focus fixed focal length imaging subsystem 3B′ anda 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). The imaging subsystem3B′ comprises a group of stationary lens elements 3A1 mounted along theoptical bench before the image detecting array 3A, and a group offocusing lens elements 3B′ (having a fixed effective focal length)mounted along the optical bench in front of the stationary lens elements3A1. In a non-customized application, focal distance control can beprovided by moving the 1-D image detecting array 3A back and forth alongthe optical axis in response to a first set of control signals 3Egenerated by the system controller 22, while the entire group of focallens elements 3B′ remain stationary. Alternatively, focal distancecontrol can also be provided by moving the entire group of focal lenselements 3B′ back and forth with a translator 3C in response to a firstset of control signals 3E generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. In customizedapplications, it is possible for the individual lens elements in thegroup of focusing lens elements 3B′ to be moved in response to controlsignals generated by the system controller 22. Regardless of theapproach taken, an IFD module 3′ with variable focus fixed focal lengthimaging can be realized in a variety of ways, each being embraced by thespirit of the present invention.

In accordance with the present invention, the planar laser illuminationarrays 6A and 6B, the linear image formation and detection module 3′,the folding/sweeping FOV mirror 9′, and the planar laser illuminationbeam folding/sweeping mirrors 37A′ and 37B′ employed in this generalizedsystem embodiment, are fixedly mounted on an optical bench or chassis 8so as to prevent any relative motion (which might be caused by vibrationor temperature changes) between: (i) the image forming optics (e.g.imaging lens) within the image formation and detection module 3′ and theFOV folding/sweeping mirror 9′ employed therewith; and (ii) each planarlaser illumination module (i.e. VLD/cylindrical lens assembly) and theplanar laser illumination beam folding/sweeping mirrors 37A′ and 37B′employed in this PLIIM system configuration. Preferably, the chassisassembly should provide for easy and secure alignment of all opticalcomponents employed in the planar laser illumination arrays 6A and 6B,beam folding/sweeping mirrors 37A′ and 37B′, the image formation anddetection module 3′ and FOV folding/sweeping mirror 9′, as well as beeasy to manufacture, service and repair. Also, this generalized PLIIMsystem embodiment 40′ employs the general “planar laser illumination”and “focus beam at farthest object distance (FBAFOD)” principlesdescribed above.

Applications for the Fourth Generalized Embodiment of the PLIIM Systemof the Present Invention

As the PLIIM systems shown in FIGS. 2I1 through 2I4 employ (i) an IFDmodule having a linear image detecting array and an imaging subsystemhaving variable focus (i.e. focal distance) control, and (ii) amechanism for automatically sweeping both the planar (2-D) FOV andplanar laser illumination beam through a 3-D scanning field in an “upand down” pattern while maintaining the inventive principle of“laser-beam/FOV coplanarity” hereindisclosed, such PLIIM systems aregood candidates for use in a hand-held scanner application, shown inFIGS. 2I5, and the hands-free presentation scanner applicationillustrated in FIG. 2I6. The provision of variable focal distancecontrol in these illustrative PLIIM systems is most sufficient for thehand-held scanner application shown in FIG. 2I5, and presentationscanner application shown in FIGS. 2I6, as the demands placed on thedepth of field and variable focus control characteristics of suchsystems will not be severe.

Fifth Generalized Embodiment of the PLIIM System of the PresentInvention

The fifth generalized embodiment of the PLIIM system of the presentinvention 50 is illustrated in FIG. 3A. As shown therein, the PLIIMsystem 50 comprises: a housing 2 of compact construction; a linear (i.e.1-dimensional) type image formation and detection (IFD) module 3″including a 1-D electronic image detection array 3A, a linear (1-D)imaging subsystem (LIS) 3B″ having a variable focal length, a variablefocal distance, and a variable field of view (FOV), for forming a 1-Dimage of an illuminated object located within the fixed focal distanceand FOV thereof and projected onto the 1-D image detection array 3A, sothat the 1-D image detection array 3A can electronically detect theimage formed thereon and automatically produce a digital image data set5 representative of the detected image for subsequent image processing;and a pair of planar laser illumination arrays (PLIAs) 6A and 6B, eachmounted on opposite sides of the IFD module 3″, such that each planarlaser illumination array 6A and 6B produces a plane of laser beamillumination 7A, 7B which is disposed substantially coplanar with thefield view of the image formation and detection module 3″ during objectillumination and image detection operations carried out by the PLIIMsystem.

In the PLIIM system of FIG. 3A, the linear image formation and detection(IFD) module 3″ has an imaging lens with a variable focal length (i.e. azoom-type imaging lens) 3B1, that has a variable angular field of view(FOV); that is, the farther the target object is located from the IFDmodule, the larger the projection dimensions of the imaging subsystem'sFOV become on the surface of the target object. A zoom imaging lens iscapable of changing its focal length, and therefore its angular field ofview (FOV) by moving one or more of its component lens elements. Theposition at which the zooming lens element(s) must be in order toachieve a given focal length is determined by consulting a lookup table,which must be constructed ahead of time either experimentally or bydesign software, in a manner well known in the art. An advantage tousing a zoom lens is that the resolution of the image that is acquired,in terms of pixels or dots per inch, remains constant no matter what thedistance from the target object to the lens. However, a zoom camera lensis more difficult and more expensive to design and produce than thealternative, a fixed focal length camera lens.

The image formation and detection (IFD) module 3″ in the PLIIM system ofFIG. 3A also has an imaging lens 3B2 with variable focal distance, whichcan adjust its image distance to compensate for a change in the target'sobject distance. Thus, at least some of the component lens elements inthe imaging subsystem 3B2 are movable, and the depth of field (DOF) ofthe imaging subsystem does not limit the ability of the imagingsubsystem to accommodate possible object distances and orientations.This variable focus imaging subsystem 3B2 is able to move its componentsin such a way as to change the image distance of the imaging lens tocompensate for a change in the target's object distance, thus preservinggood image focus no matter where the target object might be located.This variable focus technique can be practiced in several differentways, namely: by moving lens elements in the imaging subsystem; bymoving the image detection/sensing array relative to the imaging lens;and by dynamic focus control. Each of these different methods has beendescribed in detail above.

In accordance with the present invention, the planar laser illuminationarrays 6A and 6B the image formation and detection module 3″ are fixedlymounted on an optical bench or chassis assembly 8 so as to prevent anyrelative motion between (i) the image forming optics (e.g. camera lens)within the image formation and detection module 3″ and (ii) each planarlaser illumination module (i.e. VLD/cylindrical lens assembly) employedin the PLIIM system which might be caused by vibration or temperaturechanges. Preferably, the chassis assembly should provide for easy andsecure alignment of all optical components employed in the planar laserillumination arrays 6A and 6B as well as the image formation anddetection module 3″, as well as be easy to manufacture, service andrepair. Also, this PLIIM system employs the general “planar laserillumination” and “FBAFOD” principles described above.

First Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3B1

The first illustrative embodiment of the PLIIM system of FIG. 3A 50A isshown in FIG. 3B1. As illustrated therein, the field of view of theimage formation and detection module 3″ and the first and second planarlaser illumination beams 7A and 7B produced by the planar illuminationarrays 6A and 6B, respectively, are arranged in a substantially coplanarrelationship during object illumination and image detection operations.

The PLIIM system 50A illustrated in FIG. 3B1 is shown in greater detailin FIG. 3B2. As shown therein, the linear image formation and detectionmodule 3″ is shown comprising an imaging subsystem 3B″, and a lineararray of photo-electronic detectors 3A realized using CCD technology(e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-D lineimages formed thereon by the imaging subsystem 3B″. The imagingsubsystem 3B″ has a variable focal length imaging lens, a variable focaldistance and a variable field of view. As shown, each planar laserillumination array 6A, 6B comprises a plurality of planar laserillumination modules (PLIMs) 11A through 11F, closely arranged relativeto each other, in a rectilinear fashion. As taught hereinabove, therelative spacing of each PLIM 11 is such that the spatial intensitydistribution of the individual planar laser beams superimpose andadditively provide a composite planar case illumination beam havingsubstantially uniform composite spatial intensity distribution for theentire planar laser illumination array 6A and 6B.

As shown in FIG. 3C1, the PLIIM system 50A of FIG. 3B1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3″; an image frame grabber 19operably connected to the linear-type image formation and detectionmodule 3A, for accessing 1-D images (i.e. 1-D digital image data sets)therefrom and building a 2-D digital image of the object beingilluminated by the planar laser illumination arrays 6A and 6B; an imagedata buffer (e.g. VRAM) 20 for buffering 2-D images received from theimage frame grabber 19; a decode image processor 21, operably connectedto the image data buffer 20, for carrying out image processingalgorithms (including bar code symbol decoding algorithms) and operatorson digital images stored within the image data buffer; and a systemcontroller 22 operably connected to the various components within thesystem for controlling the operation thereof in an orchestrated manner.

FIG. 3C2 illustrates in greater detail the structure of the IFD module3″ used in the PLIIM system of FIG. 3B1. As shown, the IFD module 3″comprises a variable focus variable focal length imaging subsystem 3B″and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C1 in response to a firstset of control signals generated by the system controller 22, while the1-D image detecting array 3A remains stationary. Alternatively, focaldistance control can be provided by moving the 1-D image detecting array3A back and forth along the optical axis with translator 3C1 in responseto a first set of control signals 3E2 generated by the system controller22, while the second group of focal lens elements 3B2 remain stationary.For zoom control (i.e. variable focal length control), the focal lenselements in the third group 3B2 are typically moved relative to eachother with translator 3C1 in response to a second set of control signals3E2 generated by the system controller 22. Regardless of the approachtaken in any particular illustrative embodiment, an IFD module withvariable focus variable focal length imaging can be realized in avariety of ways, each being embraced by the spirit of the presentinvention.

A preferred implementation of the image subsystem of FIG. 3C2 is shownin FIG. 3D. As shown in FIG. 3D, imaging subsystem 3B″ comprises: anoptical bench 3D having a pair of rails, along which mounted opticalelements are translated; a linear CCD-type image detection array 3A(e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line ScanCamera, from Dalsa, Inc. USA—http:/www/dalsa.com) fixedly mounted to oneend of the optical bench; a system of stationary lenses 3A1 fixedlymounted before the CCD-type linear image detection array 3A; a firstsystem of movable lenses 3B1 slidably mounted to the rails of theoptical bench 3D by a set of ball bearings, and designed for steppedmovement relative to the stationary lens subsystem 3A1 with translator3C1 in automatic response to a first set of control signals 3E1generated by the system controller 22; and a second system of movablelenses 3B2 slidably mounted to the rails of the optical bench by way ofa second set of ball bearings, and designed for stepped movementsrelative to the first system of movable lenses 3B with translator 3C2 inautomatic response to a second set of control signals 3D2 generated bythe system controller 22. As shown in FIG. 3D, a large stepper wheel 42driven by a zoom stepper motor 43 engages a portion of the zoom lenssystem 3B1 to move the same along the optical axis of the stationarylens system 3A1 in response to control signals 3C1 generated from thesystem controller 22. Similarly, a small stepper wheel 44 driven by afocus stepper motor 45 engages a portion of the focus lens system 3B2 tomove the same along the optical axis of the stationary lens system 3A1in response to control signals 3E2 generated from the system controller22.

Method of Adjusting the Focal Characteristics of the Planar LaserIllumination Beams Generated by Planar Laser Illumination Arrays Used inConjunction with Image Formation and Detection Modules EmployingVariable Focal Length (Zoom) Imaging Lenses

Unlike the fixed focal length imaging lens case, there occurs asignificant a 1/r² drop-off in laser return light intensity at the imagedetection array when using a zoom (variable focal length) imaging lensin the PLIIM system hereof. In PLIIM system employing an imagingsubsystem having a variable focal length imaging lens, the area of theimaging subsystem's field of view (FOV) remains constant as the workingdistance increases. Such variable focal length control is used to ensurethat each image formed and detected by the image formation and detection(IFD) module 3″ has the same number of “dots per inch” (DPI) resolution,regardless of the distance of the target object from the IFD module 3″.However, since module's field of view does not increase in size with theobject distance, equation (8) must be rewritten as the equation (10) setforth below

$\begin{matrix}{E_{ccd}^{zoom} = \frac{E_{0}f^{2}s^{2}}{8\; d^{2}F^{2}r^{2}}} & (10)\end{matrix}$

where s² is the area of the field of view and d² is the area of a pixelon the image detecting array. This expression is a strong function ofthe object distance, and demonstrates 1/r² drop off of the return light.If a zoom lens is to be used, then it is desirable to have a greaterpower density at the farthest object distance than at the nearest, tocompensate for this loss. Again, focusing the beam at the farthestobject distance is the technique that will produce this result.

Therefore, in summary, where a variable focal length (i.e. zoom) imagingsubsystem is employed in the PLIIM system, the planar laser beamfocusing technique of the present invention described above helpscompensate for (i) decreases in the power density of the incidentillumination beam due to the fact that the width of the planar laserillumination beam increases for increasing distances away from theimaging subsystem, and (ii) any 1/r² type losses that would typicallyoccur when using the planar laser planar illumination beam of thepresent invention.

Second Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

The second illustrative embodiment of the PLIIM system of FIG. 3A 50B isshown in FIG. 3E1 comprising: an image formation and detection module 3″having an imaging subsystem 3B with a variable focal length imaginglens, a variable focal distance and a variable field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a field of viewfolding mirror 9 for folding the field of view of the image formationand detection module 3″; and a pair of planar laser illumination arrays6A and 6B arranged in relation to the image formation and detectionmodule 3″ such that the field of view thereof folded by the field ofview folding mirror 9 is oriented in a direction that is coplanar withthe composite plane of laser illumination 12 produced by the planarillumination arrays, during object illumination and image detectionoperations, without using any laser beam folding mirrors.

As shown in FIG. 3E2, the PLIIM system of FIG. 3E1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A; a field of view folding mirror9′ for folding the field of view of the image formation and detectionmodule 3″; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3″, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer; and a system controller 22 operably connected to thevarious components within the system for controlling the operationthereof in an orchestrated manner.

FIG. 3E3 illustrates in greater detail the structure of the IFD module3″ used in the PLIIM system of FIG. 3E1. As shown, the IFD module 3″comprises a variable focus variable focal length imaging subsystem 3B″and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B″ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3B2. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C2 in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. Alternatively,focal distance control can be provided by moving the 1-D image detectingarray 3A back and forth along the optical axis with translator 3C2 inresponse to a first set of control signals 3E2 generated by the systemcontroller 22, while the second group of focal lens elements 3B2 remainstationary. For zoom control (i.e. variable focal length control), thefocal lens elements in the third group 3B1 are typically moved relativeto each other with translator 3C1 in response to a second set of controlsignals 3E1 generated by the system controller 22. Regardless of theapproach taken in any particular illustrative embodiment, an IFD module3″ with variable focus variable focal length imaging can be realized ina variety of ways, each being embraced by the spirit of the presentinvention.

Detailed Description of an Exemplary Realization of the PLIIM SystemShown in FIG. 3E1 Through 3E3

Referring now to FIGS. 3E4 through 3E8, an exemplary realization of thePLIIM system 50B shown in FIGS. 3E1 through 3E3 will now be described indetail below.

As shown in FIGS. 3E41 and 3E5, an exemplary realization of the PLIIMsystem 50B FIGS. 3E1-3E3 is indicated by reference numeral 25′ containedwithin a compact housing 2 having height, length and width dimensions ofabout 4.5″, 21.7″ and 19.7″, respectively, to enable easy mounting abovea conveyor belt structure or the like. As shown in FIG. 3E4, 3E5 and3E6, the PLIIM system comprises a linear image formation and detectionmodule 3″, a pair of planar laser illumination arrays 6A, and 6B, and afield of view (FOV) folding structure (e.g. mirror, refractive element,or diffractive element) 9. The function of the FOV folding mirror 9 isto fold the field of view (FOV) 10 of the image formation and detectionmodule 3′ in an imaging direction that is coplanar with the plane oflaser illumination beams 7A and 7B produced by the planar illuminationarrays 6A and 6B. As shown, these components are fixedly mounted to anoptical bench 8 supported within the compact housing 2 so that theseoptical components are forced to oscillate together. The linear CCDimaging array 3A can be realized using a variety of commerciallyavailable high-speed line-scan camera systems such as, for example, thePiranha Model Nos. CT-P4, or CL-P4 High-Speed CCD Line Scan Camera, fromDalsa, Inc. USA—http:/www/dalsa.com. Notably, image frame grabber 19,image data buffer (e.g. VRAM) 20, decode image processor 21, and systemcontroller 22 are realized on one or more printed circuit (PC) boardscontained within a camera and system electronic module 27 also mountedon the optical bench, or elsewhere in the system housing 2.

While this system design requires additional optical surfaces (i.e.planar laser beam folding mirrors) which complicates laser-beam/FOValignment, and attenuates slightly the intensity of collected laserreturn light, this system design will be beneficial when the FOV of theimaging subsystem cannot have a large apex angle, as defined as theangular aperture of the imaging lens (in the zoom lens assembly), due tothe fact that the IFD module 3″ must be mounted on the optical bench ina backed-off manner to the conveyor belt (or maximum object distanceplane), and a longer focal length lens (or zoom lens with a range oflonger focal lengths) is chosen.

One notable advantage of this system design is that it enables aconstruction having an ultra-low height profile suitable, for example,in unitary package identification and dimensioning systems of the typedisclosed in FIGS. 17-22, wherein the image-based bar code symbol readerneeds to be installed within a compartment (or cavity) of a housinghaving relatively low height dimensions. Also, in this system design,there is a relatively high degree of freedom provided in where the imageformation and detection module 3″ can be mounted on the optical bench ofthe system, thus enabling the field of view (FOV) folding techniquedisclosed in FIG. 1L1 to be practiced in a relatively easy manner.

As shown in FIG. 3E4, the compact housing 2 has a relatively long lighttransmission window 28 of elongated dimensions for the projecting theFOV 10 of the image formation and detection module 3″ through thehousing towards a predefined region of space outside thereof, withinwhich objects can be illuminated and imaged by the system components onthe optical bench. Also, the compact housing 2 has a pair of relativelyshort light transmission apertures 30A and 30B, closely disposed onopposite ends of light transmission window 28, with minimal spacingtherebetween, as shown in FIG. 3E4. Such spacing is to ensure that theFOV emerging from the housing 2 can spatially overlap in a coplanarmanner with the substantially planar laser illumination beams projectedthrough transmission windows 29A and 29B, as close to transmissionwindow 28 as desired by the system designer, as shown in FIGS. 3E6 and3E7. Notably, in some applications, it is desired for such coplanaroverlap between the FOV and planar laser illumination beams to occurvery close to the light transmission windows 28, 29A and 29B (i.e. atshort optical throw distances), but in other applications, for suchcoplanar overlap to occur at large optical throw distances.

In either event, each planar laser illumination array 6A and 6B isoptically isolated from the FOV of the image formation and detectionmodule 3″ to increase the signal-to-noise ratio (SNR) of the system. Inthe preferred embodiment, such optical isolation is achieved byproviding a set of opaque wall structures 30A, 30B about each planarlaser illumination array, extending from the optical bench 8 to itslight transmission window 29A or 29B, respectively. Such opticalisolation structures prevent the image formation and detection module 3″from detecting any laser light transmitted directly from the planarlaser illumination arrays 6A and 6B within the interior of the housing.Instead, the image formation and detection module 3″ can only receiveplanar laser illumination that has been reflected off an illuminatedobject, and focused through the imaging subsystem 3B″ of the IFD module3″.

Notably, the linear image formation and detection module of the PLIIMsystem of FIG. 3E4 has an imaging subsystem 3B″ with a variable focallength imaging lens, a variable focal distance, and a variable field ofview. In FIG. 3E8, the spatial limits for the FOV of the image formationand detection module are shown for two different scanning conditions,namely: when imaging the tallest package moving on a conveyor beltstructure; and when imaging objects having height values close to thesurface of the conveyor belt structure. In a PLIIM system having avariable focal length imaging lens and a variable focusing mechanism,the PLIIM system would be capable of imaging at either of the twoconditions indicated above.

Third Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

The third illustrative embodiment of the PLIIM system of FIG. 3A 50C isshown in FIG. 3F1 comprising: an image formation and detection module 3″having an imaging subsystem 3B″ with a variable focal length imaginglens, a variable focal distance and a variable field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a pair ofplanar laser illumination arrays 6A and 6B for producing first andsecond planar laser illumination beams 7A and 7B, respectively; and apair of planar laser beam folding mirrors 37A and 37B for folding theplanes of the planar laser illumination beams produced by the pair ofplanar illumination arrays 6A and 6B, in a direction that is coplanarwith the plane of the FOV of the image formation and detection module 3″during object illumination and imaging operations.

One notable disadvantage of this system architecture is that it requiresadditional optical surfaces (i.e. the planar laser beam folding mirrors)which reduce outgoing laser light and therefore the return laser lightslightly. Also this system design requires a more complicated beam/FOVadjustment scheme than the direct-viewing design shown in FIG. 3B1.Thus, this system design can be best used when the planar laserillumination beams do not have large apex angles to provide sufficientlyuniform illumination. Notably, in this system embodiment, the PLIMs aremounted on the optical bench as far back as possible from the beamfolding mirrors 37A and 37B, and cylindrical lenses 16 with largerradiuses will be employed in the design of each PLIM 11A through 11P.

As shown in FIG. 3F2, the PLIIM system of FIG. 3F1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3A; a pair of planar laserillumination beam folding mirrors 37A and 37B, for folding the planarlaser illumination beams 7A and 7B in the imaging direction; an imageframe grabber 19 operably connected to the linear-type image formationand detection module 3″, for accessing 1-D images (i.e. 1-D digitalimage data sets) therefrom and building a 2-D digital image of theobject being illuminated by the planar laser illumination arrays 6A and6B; an image data buffer (e.g. VRAM) 20 for buffering 2-D imagesreceived from the image frame grabber 19; a decode image processor 21,operably connected to the image data buffer 20, for carrying out imageprocessing algorithms (including bar code symbol decoding algorithms)and operators on digital images stored within the image data buffer; anda system controller 22 operably connected to the various componentswithin the system for controlling the operation thereof in anorchestrated manner.

FIG. 3F3 illustrates in greater detail the structure of the IFD module3″ used in the PLIIM system of FIG. 3F1. As shown, the IFD module 3″comprises a variable focus variable focal length imaging subsystem 3B″and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A′ mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench 3D in front of the first groupof stationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth in response to a first set of controlsignals generated by the system controller, while the 1-D imagedetecting array 3A remains stationary. Alternatively, focal distancecontrol can be provided by moving the i-D image detecting array 3A backand forth along the optical axis with translator in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe second group of focal lens elements 3B2 remain stationary. For zoomcontrol (i.e. variable focal length control), the focal lens elements inthe third group 3B1 are typically moved relative to each other withtranslator 3C1 in response to a second set of control signals 3E1generated by the system controller 22. Regardless of the approach takenin any particular illustrative embodiment, an IFD module with variablefocus variable focal length imaging can be realized in a variety ofways, each being embraced by the spirit of the present invention.

Fourth Illustrative Embodiment of the PLIIM System of the PresentInvention Shown in FIG. 3A

The fourth illustrative embodiment of the PLIIM system of FIG. 3A 50D isshown in FIG. 3G1 comprising: an image formation and detection module 3″having an imaging subsystem 3B″ with a variable focal length imaginglens, a variable focal distance and a variable field of view, and alinear array of photo-electronic detectors 3A realized using CCDtechnology (e.g. Piranha Model Nos. CT-P4, or CL-P4 High-Speed CCD LineScan Camera, from Dalsa, Inc. USA—http:/www/dalsa.com) for detecting 1-Dline images formed thereon by the imaging subsystem 3B″; a FOV foldingmirror 9 for folding the FOV of the imaging subsystem in the directionof imaging; a pair of planar laser illumination arrays 6A and 6B forproducing first and second planar laser illumination beams 7A, 7B; and apair of planar laser beam folding mirrors 37A and 37B for folding theplanes of the planar laser illumination beams produced by the pair ofplanar illumination arrays 6A and 6B, in a direction that is coplanarwith the plane of the FOV of the image formation and detection moduleduring object illumination and image detection operations.

As shown in FIG. 3G2, the PLIIM system of FIG. 3G1 comprises: planarlaser illumination arrays 6A and 6B, each having a plurality of planarlaser illumination modules 11A through 11F, and each planar laserillumination module being driven by a VLD driver circuit 18; linear-typeimage formation and detection module 3″; a FOV folding mirror 9 forfolding the FOV of the imaging subsystem in the direction of imaging; apair of planar laser illumination beam folding mirrors 37A and 37B, forfolding the planar laser illumination beams 7A and 7B in the imagingdirection; an image frame grabber 19 operably connected to thelinear-type image formation and detection module 3″, for accessing 1-Dimages (i.e. 1-D digital image data sets) therefrom and building a 2-Ddigital image of the object being illuminated by the planar laserillumination arrays 6A and 6B; an image data buffer (e.g. VRAM) 20 forbuffering 2-D images received from the image frame grabber 19; a decodeimage processor 21, operably connected to the image data buffer 20, forcarrying out image processing algorithms (including bar code symboldecoding algorithms) and operators on digital images stored within theimage data buffer 20; and a system controller 22 operably connected tothe various components within the system for controlling the operationthereof in an orchestrated manner.

FIG. 3G3 illustrates in greater detail the structure of the IFD module3″ used in the PLIIM system of FIG. 3G1. As shown, the IFD module 3″comprises a variable focus variable focal length imaging subsystem 3B″and a 1-D image detecting array 3A mounted along an optical bench 3Dcontained within a common lens barrel (not shown). In general, theimaging subsystem 3B′ comprises: a first group of focal lens elements3A1 mounted stationary relative to the image detecting array 3A; asecond group of lens elements 3B2, functioning as a focal lens assembly,movably mounted along the optical bench in front of the first group ofstationary lens elements 3A1; and a third group of lens elements 3B1,functioning as a zoom lens assembly, movably mounted between the secondgroup of focal lens elements and the first group of stationary focallens elements 3A1. In a non-customized application, focal distancecontrol can also be provided by moving the second group of focal lenselements 3B2 back and forth with translator 3C2 in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe 1-D image detecting array 3A remains stationary. Alternatively,focal distance control can be provided by moving the 1-D image detectingarray 3A back and forth along the optical axis in response to a firstset of control signals 3E2 generated by the system controller 22, whilethe second group of focal lens elements 3B2 remain stationary. For zoomcontrol (i.e. variable focal length control), the focal lens elements inthe third group 3B1 are typically moved relative to each other withtranslator 3C1 in response to a second set of control signals 3C1generated by the system controller 22. Regardless of the approach takenin any particular illustrative embodiment, an IFD module with variablefocus variable focal length imaging can be realized in a variety ofways, each being embraced by the spirit of the present invention.

Applications for the Fifth Generalized Embodiment of the PLIIM System ofthe Present Invention, and the Illustrative Embodiments Thereof

As the PLIIM systems shown in FIGS. 3A through 3G3 employ an IFD modulehaving a linear image detecting array and an imaging subsystem havingvariable focal length (zoom) and variable focus (i.e. focal distance)control mechanisms, such PLIIM systems are good candidates for use inthe conveyor top scanner application shown in FIG. 3H, as variations intarget object distance can be up to a meter or more (from the imagingsubsystem) and the imaging subsystem provided therein can easilyaccommodate such object distance parameter variations during objectillumination and imaging operations. Also, by adding dynamic focusingfunctionality to the imaging subsystem of any of the embodiments shownin FIGS. 3A through 3F3, the resulting PLIIM system will becomeappropriate for the conveyor side scanning application also shown inFIG. 3G, where the demands on the depth of field and variable focus ordynamic focus requirements are greater compared to a conveyor topscanner application.

Modifications Of The Illustrative Embodiments

While each embodiment of the PLIIM system of the present inventiondisclosed herein has employed a pair of planar laser illuminationarrays, it is understood that in other embodiments of the presentinvention, only a single PLIA may be used, whereas in other embodimentsthree or more PLIAs may be used depending on the application at hand.

While the illustrative embodiments disclosed herein have employedelectronic-type imaging detectors (e.g. 1-D and 2-D CCD-type imagesensing/detecting arrays) for the clear advantages that such devicesprovide in bar code and other photo-electronic scanning applications, itis understood, however, that photo-optical and/or photo-chemical imagedetectors/sensors (e.g. optical film) can be used to practice theprinciples of the present invention disclosed herein.

While the package conveyor subsystems employed in the illustrativeembodiments have utilized belt or roller structures to transportpackages, it is understood that this subsystem can be realized in manyways, for example: using trains running on tracks passing through thelaser scanning tunnel; mobile transport units running through thescanning tunnel installed in a factory environment;robotically-controlled platforms or carriages supporting packages,parcels or other bar coded objects, moving through a laser scanningtunnel subsystem.

While the various embodiments of the package identification andmeasuring system hereof have been described in connection with linear(1-D) and 2-D code symbol scanning applications, it should be clear,that the system and methods of the present invention are equally suitedfor scanning alphanumeric characters (e.g. textual information) inoptical character recognition (OCR) applications, as taught in U.S. Pat.No. 5,727,081 to Burges, et al, incorporated herein by reference, andscanning graphical images as practiced in the graphical scanning arts.

It is understood that the laser scanning systems, modules, engines andsubsystems of the illustrative embodiments may be modified in a varietyof ways which will become readily apparent to those skilled in the art,and having the benefit of the novel teachings disclosed herein. All suchmodifications and variations of the illustrative embodiments thereofshall be deemed to be within the scope and spirit of the presentinvention as defined by the Claims to Invention appended hereto.

1. A hand-supportable planar laser illumination and imaging (PLIIM)based code symbol reader comprising: a hand-supportable housing havinglight transmission aperture; a linear image formation and detectionmodule, disposed in hand-supportable housing, and having a linear imagedetection array and image formation optics with a field of view (FOV)extending from said linear image detection array, through said lighttransmission aperture and onto an object moving relative to saidhand-supportable housing during object illumination and imagingoperations; a planar laser illumination beam (PLIB) producing device,disposed on said hand-supportable housing, and having at least onevisible laser diode (VLD) arranged in relation to said linear imageformation and detection module, for producing a planar lightillumination beam (PLIB), and projecting said planar light illuminationbeam through light transmission aperture and oriented such that theplane of said planar light illumination beam is coplanar with the fieldof view of said linear image formation and detection module so that theobject can be simultaneously illuminated by said planar lightillumination beam and imaged within said field of view and onto saidlinear image detection array for detection as a digital linear image ofthe imaged object; an image grabber, disposed on said hand-supportablehousing, for grabbing digital linear images formed and detected by saidimage formation and detection module; an image data buffer, disposed onsaid hand-supportable housing, for buffering said digital linear imagesgrabbed by said image grabber, and constructing two-dimensional image ofthe object from series of buffered digital linear images thereof; animage processor, disposed on said hand-supportable housing, and operablyassociated with said image data buffer, for processing said buffereddigital linear images so as to read code symbols graphically representedin said two-dimensional digital linear images; and a controller forautomatically controlling one or more of said linear image formation anddetection module, said PLIB producing device, said image frame grabber,and said image data buffer.
 2. The PLIIM based code symbol readingsystem of claim 1, wherein said PLIB producing device comprises beamforming optics disposed before each said VLD so as to produce at leastone PLIB component of said PLIB produced from said PLIB producingdevice.
 3. The hand-supportable PLIIM-based system of claim 1, whereinsaid image forming optics have a fixed focal distance and a fixed focallength providing a fixed field of view.
 4. The hand-supportablePLIIM-based system of claim 1, wherein said image forming optics have avariable focal distance and a fixed focal length providing a fixed fieldof view.
 5. The hand-supportable PLIIM-based system of claim 1, whereinsaid image forming optics have a variable focal distance and a variablefocal length providing a variable field of view.
 6. The hand-supportablePLIIM-based system of claim 1, wherein code symbols are selected fromthe group consisting of ID bar code symbols, 2D bar code symbols andmatrix type bar code symbols.
 7. The hand-supportable PLIIM-based systemof claim 1, wherein said linear image formation and detection module,said PLIB producing device, said image frame grabber, said image databuffer and said controller are supported on a single platform withinsaid hand-supportable housing.
 8. The hand-supportable PLIIM-basedsystem of claim 1, wherein said image data buffer comprises VRAM.
 9. Thehand-supportable PLIIM-based system of claim 1, wherein said imageprocessor comprises a programmed microprocessor.
 10. Thehand-supportable PLIIM-based system of claim 1, wherein said controllercomprises a programmed microprocessor.